swithing 87 cab for 84 cab

[87 3+3]

I recently purchased an 87 3/4 ton 4x4 standard cab. The body is rusted so i have gotten a rust free bed and front clip. I have found a rust free 84 cab that came off of a 1 ton that i might buy. my question is: Will this cab bolt on to my 3/4 ton frame? My other main question is: What will i have to do to this 84 cab to make it work for my truck with my fuel injected 350 and what ever else i might have to change with the wire harness? I was told i would have to switch the wiring harness from my 87 cab to the 84 cab. Is this true or is there a different/easier way? How hard even is it to switch the whole wiring harness? I am worried it will be too much for me and i wont be able to do it, i am only in high school...

Thank you.