Do some measuring. I think you'll find the S-10 stuff is too narrow for a TF truck.
The 4.3 can be thought of as a small block V-8 with the front pair of cylinders lopped off. The transmission that sat behind it should readily bolt to your 283.
1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more... It's true. I really don't do anything but browse the Internet looking for trouble...