That is a 2wd body, yes? I'll get some measurements for you. I had a 86 2wd I planned on swapping to 4wd...with parts from my ex's 89...
I did learn the 2wd floor is lower in the trans tunnel area. You might want to consider a 1 or 2 inch body lift. Or welding in a tunnel section from a 4wd unit.
Yes, it is a 2wd body. I've got the bolt in transmission tunnel part from a 4wd truck and I cut out the raised portion behind it from a truck in the junk yard. All I've got to do is cut out the corresponding parts in my truck and hopefully it'll all fit without too much modification/fabrication.