I built an engine like that 25 years ago. Crown (now out of business) made the manifolds, linkage, and air cleaners. The conversion required 140 heads, the ones with two carb bases on the integral intake manifold. The manifolds were machined off and some areas were built up with weld. Then the surface was given a final surface cut. Reall works good.

I got the 40IDA3C carbs from a contact in Germany. If you were doing the conversion today the carbs would be a major expense.

I understand Clarks Corvairs bought out the Crown stock and may have the manifolds and other accessories.

With today's technology it might be possible to rig up some kind of fuel injection for less than the price of the carbs.

I recently sold the carbs, heads, and manifolds to a guy in Mass. who is building a supper street dune buggy.