Unfortunately the 383 doesn't get the respect it deserves (IMHO). Seems that almost everyone prefers the 440 over the 383, and I understand the reasoning behind it. Even though I like the 383 I too prefer the 440. But personally I wouldn't just give up on the engine you have.
In fact, I went to look at a '69 383 HP engine just a couple days ago. I don't need it, I already have more engines then I'll ever use but I'd hate to see it end up in a scrap pile. In a few days I plan to go back with what I need to do a compression test and check a few other things more closely. If it checks out good I might buy it, bring it home and get it running then try to find the guy with a '69 Super Bee that's looking for a date correct engine. That's just how I am, but then I enjoy working on engines.
But it does make sense to face the fact that 383's just aren't in demand.
With all that said, what speed (RPM) did you spin the oil pump to get the 60 psi of pressure?
I ask because if you had let's say a 1300 RPM drill running at full speed with the oil in the pan being cold I would have expected a higher pressure reading than 60 psi.