What can I say, the 70's were apparently a dark time 
. S code '68 fastback, '70 boss 302 stripes, '68 shelby fiber glass, '69/70 mirrors, '70 grabber yellow paint, and a hole cut for a shaker hood (complete with trim ring)! The car was last on the road in 1977, the original 390 was supposedly blown up at an LA drag strip. There's still VHT tire glue splattered all over the wheel wells.
There were some cool things that came out of the '70s also, like big 'n littles, tunnel rams, nose down rakes etc. At least they didn't hack it up like lots of people did back then. Being a California car, I'm guessing it's pretty solid, which is a huge advantage. And being parked at only 9 years old, it hasn't been beat to death. Looks like a nice project.
Platigage isn't the greatest way to measure, but I don't want to be the one to tell you to tear it back down and start all over. Like Barry alluded to with the taper comment, IF you carefully checked all the mains, and ran the string from side to side of each journal, and there was a nice consistent thickness throughout the string of plastigage, I'd probably run it and just keep an eye on your oil filter for any strange particles during the first several oil changes. You're not going to be running the engine that hard with that cam anyway.
BUT, and this is a big but, you did say that the clearances came in at .0015 "ish". That .0015 doesn't leave you any wiggle room, so if that "ish" means that some were less than that, you're walking a thin line then. Remember, the clearance measurement is for both sides of the journal, top and bottom, so you only have half that clearance between the journal and the bearing at any given time. If that "ish" is more like .0012-.0013, then you're looking at only .0006 between the journal and bearing while under running conditions. That's barely half a thousandths, and that ain't so good. If that's the case, I'd be concerned and probably have the crank polished to remove another half thousandths, if it's possible to remove that much during a polish. The engine guys may be able to remark about that better than me.
Since you haven't done the rods yet, I'd be checking them before you made any final decisions. Don't consider the crank installation done until you verify that ALL clearances are good. Calling it "done" because you don't want to pull it back apart leads to thoughts of "it's good enough" when you come across something else that is borderline. Like Kevin noted, it's the fine details that are the difference between an engine that 'runs' and an engine that runs good...for a good long while. It's more work, and it's more time, but you'll be much better off, and much happier with the end result if you do.
