Needs motor

i have a 1991 chevy truck 4x4 5.7 can i put a5.3 327 in that truck will things match and will the brain work

Ask at a GM truck board.

Unlikely, your 350 is an older TBI engine with a primitive ECU. If you’re thing about one of the newer 5.3L’s (which is a 325 not a 327) you’ll have to get a new ECU. The Gen III/IV 4.8/5.3L are far more sophisticated in terms of electronics than the old TBI 350. It would be far cheaper just to rebuild what you have or buy a crate 350.