1988 Chevy Blazer motor

It will fit. But if you are asking "will it work", then the answer will be slightly different.

In 1988, the S10 had a simple, basic computer running the emission system with throttle body injection. In 1997, the 4.3L V6 Vortec has way more advance computer system with port injection system. The "new" engine will need its fuel management system and own computer for it to work properly, to say the least.