There is one aftermarket manifold for the stock 1V carb that looks like it would kick a$$. It is made by Edlebrock but is out of production. As you knwo the stock cast iron intake has sharp bends at the #1 and #6 cylinders and the runners are of un-equal length design. this makes for $hitty air flow. The Edlebrock one that I've seen had idividual runners for each cylinder and they were curved nicely to avoid dead spots in air flow. Sort of a tuned intake design. Unfortunately I've only ever come accros one and I was a fool for not buying it then.
just fyi.
Eric