Here are the differences:
92 has temp sensor in the head. 96 has the temp sensor in the thermostat, and a bolt at an odd angle in the hole in the head for the temp sensor.
92 has no studs protruding from the head or block, only bolts. 96 will have studs sticking out on 1. the ac compressor bracket 2. the front and rear of the "combination manifold". All the holes/studs are in the same places however.
92's valve cover is different.
Some of the head bolts on the 96 are studs. All of the head bolts on the 92 are bolts.
The valve springs were tweaked at some point, with the 96 springs being somewhat improved.
92 had much heavier pistons, and I believe they are of better quality, however, the 96 pistons are better from a performance standpoint AFAIK.
Just recently I swapped a 92 head and pistons into a 1996 ZJ 4.0.
Good luck with your swap.
Joe. :conceited
EDIT: it just occurred to me that the piston rings changed in 96. 92 are of standard sizes that I cant recall, and the top 2 rings are different sizes. They are of casting e234k, and are in common with certain years of Bel Air straight sixes. The 96-up pistons have metric rings, two 1.5mm top rings and a 4.0mm lower ring, i believe casting e925. Both of the standard top rings are significantly bigger than the metric ones, another advantage of the earlier engines. The rods of the earlier pistons are somewhat longer, but the total compression height is the same. The wrist pin design is also different, the earlier ones allow for some lateral play, but the modern ones do not...
I could go on and on about this, but since you're not rebuilding anyway, not much of this applies to you. But hey, you want differences, you get differences.
Oh yeah, get the exhaust manifold welded while you have the chance. It'll probably hold for a few years...