Shakey61 did a tech session on this subject at the Stovebolt Roundup here at the shop last September. Neither of us have done the swap yet but He's got the parts and we've been talking about doing it to see what we think. He might be able to to provide some input as he's researched it quite a bit. In the spring I'm planning on doing it to a later model truck I have. What year 3100 are you working on?
~Mongo


Mongo's Garage
Vintage GM Truck's & Parts
https://mongosgarage.com