your going to need an intake. The 66-69 heads used the 3/8 bolts and no angle. Your 64 (and 65, especially the early builds) used the odd 5/16 bolts at the shallower angle. I think the guy just cobbled together a 4bbl top end on a 2bbl block. Sorry. Nothing on the block will distinguish it from a 4bbl so your 'good' on the 4bbl engine restoration. Did it have a dual point distributor? Policy on suppliers was at least 2 due to strike/labor concerns. didnt want to halt the line because a bolt supplier was on strike.
