What else should be done?
 

I recently had a tick turn into a horrendous knock. Thought it was the flexplate, but after pulling the inspection covers and seeing the plate was fine I dropped the oil pan to find chunks of a piston skirt in there. #5.
First disassemble of the 4.0 I've ever done. Aside from obviously replacing the pistons/rings and bearings, what else should I do or be looking for since I've got everything taken apart?

Rear main seal and oil pump/pickup are already slated and ready to be thrown in.

Kinda bummed that I didn't quite make it to half a million miles. Was still 70k short, give or take.

Timing chain and gears.
Cam bearings.

Totally forgot that a new timing chain, sprocket, and guide came in yesterday, so that's already taken care of.
Added cam bearings to the list.

If the cam and lifters weren't giving me any issues before, can I just leave them as is?

A new cam will make better power. Old one has had many miles of use. New factory cam and new lifters will make it feel like you've got a lot more power. Swapped cams twice for new stock units & the difference is amazing. Makes taking the engine apart all worth it.

You can. Whatever you do don't mix an match the lifters. Ever. Each lifter and cam lobe have worn together to make a perfectly matched pair. Swapping them makes them wear vert quickly.

Rics suggestion is the best way to go even if it's not quite in the budget.

In either case a good assembly lune with molybdenum disulfide needs to be used to avoid dry start and lobe flattening.

Does the old cam have less lift due to wear on the lobes?

That and also wear on the bottoms of the lifters where they ride on the lobes.

Even if still "working", why would you want to put parts with half a million miles on them back into your rebuilt?

You'll want the machine shop to install new core plugs while they're boring the block for your new pistons on your half million mile block...

And core plugs, AKA freeze plugs, are available in brass.