My truck originally had a 4.3L gasser auto, and I removed that to install a motor from an older diesel S10, along with the diesel transmission.
The original 4 cyl gasser transmission will work with the diesel, but you need the bell-housing from the diesel transmission to bolt to the gas transmission. Or, you can just use the diesel transmission, as it is basically the same as the gas transmission, other than gear ratios and bellhousing.
My truck is a 1991, and it fit in just fine. I think it should fit in up to a 1993 model. I'd love to know if the front frame is the same in the newer series of truck, cause thenit shoud fit there too. My Sonoma comes with more sound-deadening material, so it is good with the diesel, which is noisier and shakier than any gas engine.
Does this help answer your question any better?