Will a TH 700R-4 transmission fit in 1991 Chevy suburban 4wd with 350 motor?
No, a TH700R4 will not directly fit a 1991 Chevy Suburban 4WD with a 350 motor. The 1991 Suburban 4x4 used a different transmission, the 4L60E (electronically controlled). While both are four-speed automatics, they have different bolt patterns, input shafts, and overall dimensions. You'd need significant modifications (highly impractical and not recommended) to make it work. Sticking with the correct 4L60E is the only sensible option.