so what exactly is the problem? the toyota trannies are pretty stout... and can handle quite a bit of abuse, plus they are easy to find someone whos got one also.... i jsut replaced my tranny, yesterday in fact..... my truck has a 22r, and its 2wd..... i broke the output shaft due to one main reason, not that it wanst strong enough, but because i drive, well, very spirited.....
i have never seen an adapter to convert a chevy turbo hydamatic 350 to the toyota 2Xr series engines... that tranny is really overkill for an engine pushing maybe 130 hp with mods.....
if it matters, my truck is a 85 with 22r pushing a tad over 100 hp, 31" tires, and 3.07 gears with a marlin 1600 conventional clutch.....
toyta made things similar.... you can swap in a tranny from an old supra.. a w58, the hgearing changes a little bit, but a negligible amount, and its stronger... you will need to drill a new hole in the floor for the shifter as its a little further back however... but everything else will bolt up as long as you swap the bellhousing form your current tranny to the supra tranny.....