Alright, I blew the transmission in my lowered 1997 Sierra. I have a 1989 350 TBI and 700R4 transmission. What would I need to do in order to swap out my 4.3L Vortec with the 350 TBI? Will my speedo cable still work with the tranny? What computers and such will need to be removed. Any help would be greatly appreciated.

totally not a good idea,totally different wiring , vortec cpi to tbi and 4l60e to 700 r4, you have no speedo cable all electric.it would be so much work and you would end up with a truck worth 1/3 of its value
sell the 350 and 700r4 and get your tranny rebuilt , a brand new 4l60e is only about 1500.00 so a rebuild should be about 1000.00. way cheaper than doing a swap

What years of 4L60E will work? I found a 94 from my buddies truck, but I dont wanna pull it unless it'll work.

94 should be no problem, check on the drivers side of the trans , it should have a round plug with about 13 pins, if so all good and swap out your control unit on the side and you are done