The process we use on all engine/trans/rearends, etc. Clean the crap out of it!!! Use degreaser or similar and get it clean. I usually have a piece of scotch brite and I get in all the little nooks and cracks! Then get some wax/grease remover and wipe her down, even a second time is recommended on used parts. On bare metal you NEED a good "etch" primer first, then you can follow with a sealer, then base/clear (or single stage).
All automotive paints/clear will take any heat a motor will create. As long as the "prep" is done correctly the finish will a long time.
