I say go for it! Engine, trans, t case, ECU, keep the frame and build on it or start a chassis from scratch and have fun!
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1980 Toyota Pickup SR5, 4x4 w/20r - Kept stock & sold
1984 Toyota Pickup, Extra Cab, 4x4 w/22R - Lifted, wheeled, broke, fixed, wheeled, broke (that repeats a lot for this one...) sold.
1986 Toyota Pickup SR5, Extra Cab, 4x4 w/22R-E - Kept stock & stolen

2000 Toyota 4Runner SR5, 4x4 w/5VZ-FE - Keeping mostly stock... plans TBD.