will an 88 T5 bolt to an 84 5liter?

Yes, the clutch will work fine, but you have to switch out the flywheel. The stock 84 flywheel is 10 inches... So obviously you need a 86-93 10.5 inch flywheel to use the 10.5 clutch. Also, yes... an 88 T-5 will bolt up to your 84 5.0 perfectly, no mods as long as it is a T-5 already.

Nick
 
I don't have any experience with this type of swap personally, but I would double check the pilot bearing diameter and the output shaft sizes as well.

I'm sure one of these guys can address both of these from memory.
 
Not sure if the 84 came with the S-rod trany, but i think it did. In that case you need a different bellhousing to mount the t-5. The S-rod bellhousing works for the S-rod trany and the Tremic. If that is the case, I am sure you can find someone willing to swap bellhousings with you on the classified section.

Mario