well I just got done doing a 4.3 swap in place of my 2.8. its not that hard actually. just need a 4.3, ecu, wireing. for the main parts. you will probably need diff springs for the front and the 4.3's exhaust components. motor mounts i am not sure what the 4 cyl has for em as with radiator.
its not that hard of a swap if i can remember any other things i will let ya know.