That's a really nice frame, but there is no need to go back with original parts if someone out there is willing to outspend you on them. There are tons of parts available that will make little difference in the bike's value, or it's rideability, whether or not the overpriced OEM stuff.
Your main issue is not going to be a crankset, anyway. It appears to me, with no braze-ons, that you'll first need to decide on a shifting system, and as an extension of that, a cable guide configuration and with it, possibly a FD requirement. Everything else is pretty much bolt-on once you make your decision.
As far a Sugino cranksets, you can buy a whole bike with what you need for half of what they want for some of those cranksets. The Sugino cranksets on many mid-80's bikes are just fine. You can get a donor bike and swap over, or buy a group of parts. There are adapters out there for the cable stops/cable guides/shifters you choose, but you'd need to choose.
Good luck with the build, it's a fine frame, but I wouldn't worry so much about a crankset someone wants to sell for $300.