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I have obtained several core engines with anticipation of rebuilding one.

I have a 79 J20 with manual valve body TH400, 203/205 doubler, 4.56 gears and 42" tires. I currently have a crane energizer 272 cam, edelbrock performer intake, long tube headers and dual 2.5" exhaust. For heads it is sporting the screw-in stud style 58cc chambers.

Years ago I had a converter shop (now closed) do a stall converter for me and it's working OK. RPM in gear is 650 and above 1k when accelerating from stop. This should change though once I throw some CR at the engine?

We have been wheeling in the snow quite a bit this year and I'm having to generate some serious wheel speed to go anywhere. I'm using 3rd gear in the trans while in 4:1 and holding it pinned. It's working pretty well but like everyone else more power is better!!

My existing engine is very tired. I had to add a catch can to the valve covers to mitigate the blow-by.

For my rebuild I am a little torn on what configuration to shoot for.

I have access to the later 63cc chambers on a couple of my cores.

I'm shooting for 10:1 CR and a cam suited to the style of off-roading as noted above (wide open)

The 343 pistons seem like a good option but are cast.
Wisecos can be had for same money but require .030 overbore ($$)

With Wisecos @ .030 and the 63cc chambers I am a lil high for my CR goal but maybe the correct camshaft will keep the DCR down so I can still run pump gas.

With 343 pistons and stock bore I am right at my CR goal as well

For cam I was looking at the 280H but I am open to suggestions

I'm looking at Mollnar rods or FalconGlobal depending on funds.

Since it seems you like to run around at or near WOT, I would suggest the 280 or larger and the oiling mods. The argument over which head to use favors the 58CC heads with the studs. The later heads use 5/16 bolts and cannot deal with the lift and spring pressures required to run a cam with more than .500" lift.
Of course, if you retard the cam timing by about 4 degrees, your low RPM cylinder pressures will be lower thus less chance of pinging/detonation with pump gas.

Back in my day the trick was to use 400 Chevy pistons with an overbore and wrist pin mod. With the 63CC heads it worked out very well on pump gas.

I'd keep it simple. Run the later heads with 343 pistons and a Victor/Torker intake manifold. This manifold gives up a little off idle but pays big above 3500 RPM.

Still kinda torn...I hate cast pistons but lots of guys have had good luck with them. I just worry about detonation on a wheeling rig due to engine load changes and potential overheating when ragging on them....

The early 58cc heads are out of the question due to the CR.

Guys are doing LS rockers now by cutting the bridges and swapping the M8 bolt for a 5/16. Stock LS is also 1.7 ratio. So it makes the later chamber heads a little easier to work with from a 'performance' standpoint.