any chevrolet transmission will bolt up to the 4.3, it probably came out with a 200r4 which is a light duty version of the 700r4. It has less clutch packs and lighter duty parts.
TH 350 is probably your best option for the least amount of money, you could then run a gm t-case or buy the adapter to bolt it to a toyota t-case, which will cost about 500 if you buy it new,
a stock th 350 will be more than enough tranny for your 4.3, there are only 2 variations of this trans, lockup and nonlockup, nonlockup is cheaper and less complicated. Think it over before you make any hasty decisions. weigh your options against each other and see what kind of logic you come up with. if you would like to see some pics of my truck, with TH350 installed I can post some
