I did carb rebuild and tune up on my 370 after an hour drive. Test drove the truck after the work and lost oil pressure about 5 minutes later [ I knew it was catastrophic]. Was conned into putting a high volume pump in. I have enough pressure to keep the bottom end from rattling at 2000 rpm but zero at idle. A machine shop told me the only place to lose pressure like that is for a cam bearing to come out. What say you? Thanks.

Dave

 

First change the oil filter. Seen them cause this problem. It can also be the bypass in the pump is stuck open. I suppose it is possible for a cam bearing to come out. But I haven't seen it in all my years of wrenching on big block Fords.

 

Bent pushrod or broken lifter could cause loss of oil to top end.
This fits with your "immediate and catastrophic" pressure loss.
makes more sense that a cam bearing coming out.

Only a guess.