To answer my own questions, I found this site:
http://www.dakota-truck.net/infosheet.html
It lists a lot of info on the Dakota’s, hopefully it’s accurate and helps others.
Seems 87-90 used the 5 on 4.5” bolt pattern, and 92-96 had the better V8
The rear end has 3 ratios, 3.21 found in the V6 & V8, 3.55 found in the 4 cyl optional on V6 & V8, 3.90 was an option for V6 & V8.
V8’s came with either a 46RH auto or a NV3500 man transmissions
WB is 112”, track width is 60.8 both are a bit longer and wider than PH, but not by much.
The PH WB is 108”, can’t seem to locate track width, but from others posting their projects, it seems to be about 4” narrower, so 56”ish.
The Dakota chassis kicks up behind the cab, so a full chassis swap means reworking the bed mounting of the PH. Going with just a front clip eliminates that work.
So for myself, definitely leaning towards the front clip of a 87-90 dak, with all the running gear.