they are both 4.3L the sierra one though is non - vortec while the 97 jimmy is a vortec.

Any way they would work?

 

There are A LOT of differences. The largest of which being the presence of a balance shaft in the '97 motor and the lack there of in the '90 motor. The blocks will be somewhat similar, but you would have to swap over A LOT of parts to make it compatible. Your best bet is to find a '96+ engine to use. If you get a 98+ engine, you will have to use the lower intake from your '97 motor as the 98+ engines do not have the temp sensor in the water neck near the thermostat.