Yes. The original 4.3 is the 5.7 with the front two cylinders removed - it will bolt right up to the transmission, and accept the wiring harness. You will have to swap the Blazer's computer with one from a truck that had the 5.7 though.
Will a Chevy blazer engine fit in a Chevy s10 pickup
Yes it will fit.
An alternator from a 2000 Chevy blazer will fit a 2002 S10 blazer with a little fabrication.
Will a Chevy Blazer engine fit in a Chevy s10 pickup
Yes
Yes
as long as they have the same engine, drive train, and ecu? sure
No.
Yes. Very easily. They are built on the same body, but the blazer is the suv and the s10 is the truck.
Will a 2000 blazer transmission fit a 1998 s 10 chevy 4x4 truck
No it will not SORRY.
Yes