Jim, one thing I see that is not correct on your post is that the VIN numbers were not stamped on Pontiac blocks until '68.
Ben, look at the heads on the engine, between the center two exhaust ports there will be cast into head numbers and/or letters that can tell us what heads are on it. Examples are 16, 96,7K3, 670, 6X, etc. Between the casting date of the heads & the casting code it will help determine what engine you have.
Steve
