GM TH350C Transgo Reprogramming Shift Kit Shift Lockup. SK 350C-1&2. FITS: THM 350C 81-91 With Lockup Torque Convertor. Fits lockup 350C transmissions. Does not fit 250C transmissions. FEATURES: Automatic Shift; Street or Full-race; Holds 1st, 2nd and 3rd to any rpm; Back shifts to any gear at your command. Total cure for soft 2-3 shift and direct clutch failure.