Either piston will result in a stack dimension of 10.286", so cut the block decks to 10.295" block deck height, then use the 0.041" gasket thickness to set the squish at 0.050". There looks to be enough flat material around the perimeter of the crown to mate up with the underside of the head to form a decent squish. Blocks '68 through '71 will have a stock block deck height of 10.300". '72 and later blocks will have a stock block deck height of 10.320".

Use an Edelbrock RPM or Weiand Stealth high-rise, dual-plane intake manifold. You'll be down about 15-20 hp with the 650 as opposed to a 750. Use quality, long-tube, tuned headers, 1 7/8" primaries. Shorty headers are a waste of money. You might just as well use stock, cast iron log manifolds.