Im planning on dropping a 502 into my 71 chevelle, it already had a 454 big block in it so the mounting points are the same. The drivetrain and suspension is already modified to handle the changes, as well as fuel system. What im wondering is what other modifications will be needed? can anyone please tell me?

fuel pump, the 502 may not have a place to mount on the block.

You'll also probably need an oil pan to fit the Chevelle chassis.

Thanks, ill keep that in mind.

Also, if its a manual transmission, I think there's a special bracket needed (no ball stud provision on the 502)...

Will the 502 need a new flexplate/flywheel?

The Ram Jet 502 comes with a flex plate. You will need another oil pan too.....