Help! Need Engine info on my B2600 4x4

I bought a "Barn Find" 87 B2600 4x4. Engine all apart, sitting in the back, all rusted up. I have heard that the 2600 is a poor excuse for an engine, so my question to you is this- is there any other engine that will bolt up to my 4x4 trani? Or, is
there an adaptor that will let me put something else in there?
Would like to put a v6 of some kind and stay with carb.