More front spring questions

[Phils67]

My j20 axle swap on my j2000 is coming along nice and near ready to go in.
1) are front lift springs designed for stock spring under axle setups? I am changing my original thinking on the build and currently have 4" rear springs and a setup that net me around 5.5-6" total rear lift and want to run 34x9.50-16 narrow TSL's. I plan to move the springs under the frame in stock configuration for now and run spring under axle, I can always add FSSR and SOA at a later time if I want. For now I want to keep it simple.
2) can someone tell me how far apart I need to weld the rearward spring mounts for the front springs? Like what is the straight line eye to eye distance on a stock, and from bottom of the rail to center of the eye on j10/j20's spring mounts also so I can keep a stock castor with these springs. I plan to weld the front mounts right at the front of the frame rails and would like stock shackle angles
3) which spring manufacturer do you recommend for the best results. Ride quality is more important to me than offroad ability because it won't really see much offroad. It's a 4.0 inline 6 so the spring rate would need to be comfortable with about 600lbs under the hood with all the add on accessories.
I'd like to get the springs/shackles/brackets addressed before I get the axle off of the bench and remove the old suspension and axle so it's not sitting on Jack stands while I wait weeks for suspension parts to show up. If the mounts are welded in place before I remove the old stuff it will make installation of everything go quicker and easier. I want the front to be like the suspension mounts were assembled at the factory and lift the front accordingly to match the rear. It doesnt need to sit level. I'm ok with it being a little bit ass-high because it levels out when there is weight in the bed.

[Phils67]

45.75" center of eye to center of eye, measuring in a straight line, is what I found elsewhere on the internet. Can anyone confirm this please? I don't think I am asking very much here. I found a wagoneer frame blueprint online and want to ensure it is accurate before I do this

[Cecil14]

I'll be home this weekend and can get some measurements for you.

For your questions:
1. Yes, lift springs (at least for the '74+ years) are designed in an SUA fashion.
2. Will measure when I get home.
3. Can't really comment on manufacturers. Skyjacker used to be lauded as an amazing ride for a 4" lift, not sure if that's still the case? If you want stock springs, a local spring manufacturer should be able to set you up. If you're looking for something online, I have ordered from General Spring. They were great on the phone. They don't build all of their stuff, so if you are concerned about origin, phone them up and ask about specific products.

[Phils67]

Ok thanks. I know I have bashed them in the past but I was looking at the Hell Creek front springs for J10/J20 last night since that's the brand I have currently with the post style. I like the rear but have never liked the front. Also been thinking more and more about using a front drop box style spring mount and doing pass-thru-frame style rearward mounts like a GM truck of that generation. WFO Concepts makes a pretty stout setup for the front mounts that are a 31.5" spring center which is basically the measurements I gather going off the spring perches on my axle. If you can double check that distance I would appreciate it. Center to center of the springs. I am not 100% decided just yet how this is going to go. Too much time on the internet and not enough time in the garage the last few days. If I go with the HC springs I think a 4" with the other style mounting points will get me sitting close to level unloaded. I really just need to start drinking more beer so I will buy expensive stuff without second guessing it and build it all with whatever shows up in the mailbox lol.

[Cecil14]

I haven't forgotten you, just haven't had a chance to sneak out and take the measurements. Will try to get to it over the next day or two.

[Phils67]

No worries. It's been like 10 degrees here so I haven't been working on it lately

[Cecil14]

Alright, here we go:

The front mounts are 32" apart:


The bolt is 2" down from the frame rail:


Front shackles are 3" long:


The front and rear hangers are 45.5" apart from front to rear:


Again the bolt is 2" down from the frame rail:


Let me know if there's any other measurements you need.

[Phils67]

Thank you SO much! You just made this so much less stressful for me. Only other question I think I have is how far from the front of the frame to the center of the front eye and what is stock spring length eye to eye? Only reason I ask on spring length is because I hear aftermarket springs aren't always the correct length so with some simple math I can compensate for any variances in fitament. I think if I get the rearward mount correct I can adjust the front forward/backward slightly to get shackle angle right and that should keep my castor pretty close to stock

[Cecil14]

The front mounts are flush with the front of the frame, I'd guess about 2" from the frame edge to the center of the mounting bolt.

My front springs are not stock, so I wouldn't trust the measurements. General Spring (https://www.generalspringkc.com/product_p/97-372.htm) lists the measurements as 22-1/2" x 24-1/2". I believe the longer side goes to the back, but I wouldn't swear to that. I can measure mine tonight to see which side is longer. My springs are real close to factory, axle is pretty centered.

[Phils67]

I can figure out the springs once I order them. My main concern was the mounting points and I can not thank you enough for all of your help! If we ever meet in person someday, the beers are on me

[Cecil14]

Ha! That's what we're all here for, right?

I just double checked some things, and the front spring mounting bolt is 2-3/8" from the front edge of the frame. Keep in mind, if you're using an older frame, that measurement may not be exactly what you want. I can throw an angle finder on my shackles tomorrow, if you want, but again not being stock and being pretty worn out, I don't know how valuable that number will be to you.

As to spring orientation, my springs have the longer side to the front (shackle side) and the shorter side at the fixed mount. The axle is pretty centered, but has a bit of room to flex and not be way forward of center. If the longer side were to the back, the axle would be way too far forward, hitting the fender and throwing the steering linkage and sway bar mounts off.

[Phils67]

What is a sway bar? Lol
I am comfortable with the info you already gave me. No need for more at this point I dont think. I'll be starting the mounts and suspension soon and hopefully by summer the whole swap will be finalized. Thanks again for the help