the engine is basically the same as a 289/302 that came in vintage cars with minor changes. for instance the timing cover and oil pans have a few differences. some timing covers from that time were cast without the fuel pump mount as EFI engines used electric pumps. some oil pans have relocated sumps that wont fit your early chassis. another issue with timing covers is that some either had the dipstick hole blocked off, or eliminated entirely. later blocks had provision for dipstick openings on the drivers side about halfway to the back of the block to work with the relocated oil pans.
there are other issues as well like some 5.0s from that time had a different balance factor, 50oz as opposed to the earlier 28oz. and of course there is the EFI system. some later engines had distributors where the advance system was completely locked out, you couldnt even change the initial timing as that was all controlled by the computer.
none of these and other minor issues are insurmountable though, for instance, you just need to change the oil pan to the earlier front sump style if yours is the rear sump pan. as for the timing cover, examine the one you have now as you might be able to use it. for instance the dipstick hole on a late model timing cover i am going to use on my 289 was plugged with a little freeze plug that popped out easily. you might also be able to drill a new hole as well.
engine mounts are going to be the same as the ones for the early chassis. wiring the EFI if you want to keep that isnt that difficult, and there are aftermarket harnesses just for that. or you can swap to a carb intake and earlier distributor if you want as they swap in place with no issues.
as long as you are using the whole engine and transmission, the balance factor is not an issue except when buying parts, so know which balance factor you have.
the rest is detail stuff that like any engine swap you have to deal with, throttle linkage, etc.