Does anyone have a part number for a melling oil pump to fit a 377 mpi motor. serial is 1a3000and something. Trying not to buy the merc pump. Also does the pressure spring need to be replaced with a stiffer one if I get a melling ..thanks for any input

Never mind ..figured it out

If I recall doesn't Melling list the M55 or M55 HV for the small blocks and I know the M77 is for big blocks 4 sure or did they change it to using the M77 for small blocks also

Why don't you post the info you found so that someone doing a search for the same thing can see the answer.

That is what tech forums are mostly for.

It's a melling 155 for the later vortec smallblocks with a 3/4" pickup/screen....A purple spring is a 70# spring which in the real world is probably 60'ish running pressure