How can I find engine and drive options going back to the 302 and 311.

No

Check formula's web site under vintage boats, i'm sure the brochure for that year will tell you.
Hope that helps

I have heard of only one never saw it but heard there was a 87 311 in NH with 375 HP SBC with KAAMA drives that was an available pkg but I did not think in a 311. dude swore up and down it was original.

How hard is it to winterize a pair of big blocks in a 302 or 311. Im in good shape but im still 61.

plenty of room

There is lots of room in front of engines on 302, as the seat slides forward and even out if you want that. Sides of the BB's are tight as in any non-staggered BB twin engine boat. But there are things you can do to make winterizing easier if you ever have to pull the engines, such as putting drain hoses on the oil and cooling system that you can access easily.

I know of an '82 302 that came from the factory with small blocks and Arnesons.