What should I do while my engine is removed?

I have a 99WJ engine that I am putting into my 95XJ after I swap the 95 head onto the 99 block. The block came out of a wrecked 99WJ (iirc with low miles).

I don't want to complicate this project too much simply because I am VERY new to this and really really want my Jeep back on the road. I've been without for about 2 years now.

That being said what thing should I do prior to installing my new engine. I've thought about changing the rear main seal on the engine, taking the transmission somewhere and let them look at it (maybe get a shift kit), paint the engine, paint the head, paint the engine bay and all kinds of things but truth be told I want to delay this project as little as possible.

So, what are the bare minimum things that it would be FOOLISH to install an engine without doing? Please bear in mind I am a noobie.

Clean everything thoroughly, inspect the steering shaft for worn rubber joint, pull the upper control arms and have them boxed for extra strength, check suspension bushings for wear, maybe take the radiator and have it cleaned out and repainted. Have fun.

Replace engine mounts

Find new header and put it on while the engine is outside

I just went thru this same thing a month ago. I replaced the intake/exhaust gasket, thermostat, radiator, hoses, water pump, and seals, i.e. oil pan, mains, valve, etc. Inspected/found/fixed two crackes on the exhaust manifold. I also degreased the entire engine area. Look for any wiring issues, i.e. broken insulation. I wish now that I would have painted the motor and engine area. Theres always next time!

I second the suggestion on the motor mounts!

X3 on the motor mounts and the radiator. Another thing to check and maybe change is the trans mount. Mine was bad and a year later still have not changed the darned thing and it rattles at idle badly.

replace exhaust manifold with aftermarket as they always do and will crack. Fixing/welding them isnt gonna work as they will only crack again, tried it and ended up replacing it.