That being said - Look at the lower (and upper) intakes - on some swaps, the intake(s) need to be changed, and that makes other things complicated.
If you have a distributor, and late 2.3/2.5 head lower intake will not fit with the distributor/brackets/accessories of the early engine.
The HEADS THEMSELVES are interchangeable, without modification.
Swapping entire engines needs to be approached with caution - Going from a DIST to EDIS requires repinning (at the minimum) to a complete harness/computer swap.