Slant 6 mod's
There is no starter clearance problem with the Dutra Duals. That's only with the "Dual Dutra Dual" installation, a race-only setup that uses two front manifolds. The twin-carb setup is only one of many induction options, and it may not be the best one…ask around; talk to people who have actually used it. Kickdown and choke with that twin Weber setup is strictly a "do it yerself" affair.
You're correct about what is necessary for an in-car cam swap.