A side draft may not be out of the question. I thought about getting some kinda air-gap manifold and cutting everything out except the bottom plate and flange area, then weld in some tubes to cross over and sit the carbs on the oposite side valve cover area.

Are those 2cyl motorcycle carbs 1 throat or 2?
All 1 throat

Are the cylinders the size of mine individually or combined?
Each

If a carb is going to feed a 25 cubic inch 1 cyl @ 10,000 rpm it should feed my 50 cubic inch cylinder @ 5000 rpm, is that close to correct?
Yes, I know that's what the "formula" shows, but it doesn't work. The small cylinder need a small carb or it has poor response, the big cylinder needs a big carb or it has no power.

Cutting off everything but the flange and chunk of the runner and extending them across is exactly what a 1960-61 Chrysler long ram runners look like (except they ended in plenums). There are also Moon Weber manifolds like that - there's no other way to hide the length and put the hood on.

I agree - it's a lot of trouble without much gain - and that's if you get it right. Most people give up after much $$$ and &<?$@~`**!!!!.