can a 2003 gmc 5.0 engine fit n my 1992 blazer 350

The 2003 engine is a 5.3 Liter LS series engine. It will not work with The 1992 blazer unless you are thinking about a complete swap of the drivetrain and engine management systems. Then you will need a LS swap mount kit.

Lq4 (6.0) are swapped into blazers and s10 all the time, the 4l60e transmission is same for v8 (not all v8s but can handle v8 power) you can make a stand alone em from you're current one, axle should be fine as these also came in v8 cars, be smart to change gears though, trans just depends if theirs an adaptor that can allow you to use stock or nv3500, or go older like 700r4 (it's a 4l60 just not electronic which is why the new ones are 4l60 (e), or get one with engine) , probley have to fab up motor and trans mounts and crossmember for trans, not cheap but not as expensive as believed, just do all you're research and gather all parts before you begin the swap, good luck