Well, I made it home Friday to find the parts on the front porch and installed everything in about an hour. I decided to crank it over to listen for any unusual noises and it sounded fine. However, I started second guessing myself and pulled the #1 plug to make sure I had it on TDC and none of the chain marks would align as they were after turning the engine over by hand.
I figured it was only an hour so I would start fresh Saturday morning, I worked 12 hours total before I fired it up Saturday and the cam chains sound fine which is silent, but it was running crappy and I found a vacuum hose un-plugged. I reconnected the hose and let it idle watching the oil pressure and temperature and all was good until I noticed a huge pool of coolant running down the driveway and found a coolant hose un-plugged, there is a lot of chit on this engine!
The oil pressure looked fine and temperature looked fine so I took a spin to the back of the neighborhood, about 1/4 mile and the temperature shot up, this was most likely due to the t-stat not being open and air pockets in the system.
I had it topped off with coolant about thirty minutes later so I took it down the highway to gas up and before I made it home, the electric fan was running continuously and the oil pressure was dropping to almost 0 and the light was coming on, I could hit the throttle and pressure would rise and the light would go out.
So, the motor sounds great and I ran it hard a few time to just below redline at 6K with no issues.
I am not sure about the oil pressure and temperature. The e-fan is supposed to be on at temps above ~208 or when the AC is on high, the mechanical fan (it has one of each) seemed to be spinning slow but I was not having overheating issues prior to the work so I doubt the fan clutch died. I ended up using the original water pump after buying and installing a defective aftermarket pump, the original pump was fine, but I did replace the t-stat with an aftermarket 170 deg although the factory rating is 180 deg.
The Frontier/Xterra's are known to have chitty oil sending units and I have replaced mine before, I suspect there is not an oil pressure problem with a crank driven mechanical pump so I will pull the sending unit and clean it. I am also pulling the pan to make sure there is no sludge or debris blocking the pickup screen, pretty easy to do on the Frontier.
I may go ahead and pull the aftermarket t-stat and put the original back in or buy a new one at Nissan tomorrow, both worked when tested in the kitchen but other than the chain set, all the original parts will be back in and it should not be running hot.
At least the Cherokee gets me down the road and back and has not failed to start, 2K miles so far