Great progress, great thread!
I vote for the 4.3 V6 also. It is a somewhat torquey engine for the displacement, and there are a ton of parts out there for them. They also get good milage if the RPM is kept down. V8 SBC con-rods don't interchange with the 4.3 V6. The big end is narrower on the V6 rod, due to the split journal even-fire crank.
mv