87 GMC 2wd cab to 78 K20

[78K20]

I've got a 78 chevy 3/4 ton 4X4 that needs a new cab.
I bought a southern 87 GMC Sierra 2wd with no rust to use for the
new body.
I was comparing the dashes today, and noticed that the dash covers
are different. I'd like to use the old dash out of my 78 on the 87 cab.
Is the metal under the dash cover the same on both cabs ?

I'd also like to use the seat out of my 78 on the 87. Are they a
simple bolt on exchange ? I had my seat in the 78 reapolstered
in vinyl so my dogs hair wouldn't stick to it. Besides, the seat in
the 87 is cloth and has cigarette burns in it.

In fact, the truth is, I MUCH prefer the look & style of everything
on my 78 4X4 cheyenne over the 87 GMC Sierra. What I'm trying to
do is restore my 78 to look like it did before the rust belt got it.
The 87 GMC I bought is rust free, I just think it's boring in the looks
department.

Anybody done a switch like this that can give me any constructive
input ?

Thanx,
78K20