5.0 to 4cyl swap ques.

First off i think you got the title wrong (5.0 to 4cyl swap ques.). Should be 4cyl. to 5.0 swap ques..

I would put rear main seal in. And any other gasket that are leaking.

bravo on finding a doner car, that will help alot and make your swap a good one. it's pretty much all straight forward just remove what you won't need from the 4 banger and replace with the "new" 5.0L stuff.

To answer your question, yeah the oil seal is a good idea, as mentionned, since it's not an easy job once everything is in place. Change the clutch, and throw-out bearing also... O2 sensors is also a good idea...

Basically be patient and do one thing at a time. Just post if you have any questions.

good luck

The key to this swap along with all other projects is one thing... PATIENCE. Trust me, this is one project that you don't want to get into a hurry with or you will be kicking yourself later. If you really don't know the condition of the engine it might be a good idea to do a rebuild. It really depends on your budget and your overall goals for the car. If you plan on throwing on a power adder in the future it would be worth the time and money to get the engine ready for that now. I would suggest to at least replace the oil pan gasket with a 1 piece rubber gasket and the rear main seal.

go ahead and put a new shift shaft seal in the tranny while you're at it,and a new trans filter/pan gasket too!