Hmmm.. If they're both carbureted, there isn't going to be much that's controlled by that ECM. Maybe an electric fuel pump.. I think the electric fan is run from a temp. switch on the intake manifold. The tach signal is going to be different, but you should be able to fix that with a little fancy soldering - I think you only have to replce a capacitor on the circuit board of the tach (if you have one)
I don't know.. I would hook it up as close to the original V6 as I could and see what happened.
When life hands you lemons, ask for tequila and salt