The only problem with #16 heads is knowing for sure which set you are talking about. There were three differant #16 heads and each set was differant. One set was small valve push in studs ('69). One set was large valve screw in studs ('68-69) and one set was round port ('73-74). The large valve screw in studs should bring around 400 for the set. The rould port (which was Super Duty) worth around 2500. The #16 head is a good head to use use to build power with if it is the round port or the large valve screw in studs. Otherwise a boat anchor would be just as good.

As far as the 670 heads they are a closed chamber head from 67. I've always like them. If you read about them they say to open the chamber up and then they are one of the best D port heads. The 16 and 670 are 72 cc heads or at least that is what Pontiac put out. If you want originallity then the 16 for '68. Just my $.02 worth on them.