Oh crap!! :-( I so can't believe that I missed they were Boss heads. Thanks for the detail info, I just don't have the patience to document that much. When I was researching mine that was one of the things I looked at and why I went with the Gen2 heads. They are essentially Boss heads stock and then do benefit from porting. I'll dig up the flow numbers for you. I found 2 guys that worked the Boss heads and there was not much they could do maybe got a bit of low lift and then a few CFM (10) if I remember at .550.The heads are the Boss 302 ones that already had the CNC program on them. Since I'm in a power/weight regulated class and didn't have infinite budget, I left that alone. I've not seen clear cut HP numbers for porting over boss head; there's flow gains for sure, but I hadn't personally been able to quantify a HP:dollar ratio for the work. Its certainly something I can explore down the road whenever its time to refresh this mill. I'm certainly happy to see anyone else's data; just none was available that satisfied my curiosity at the time.
Going back with what is known today, if anything I would consider the GT350 heads and a 5.2 block for what was spent and pick up the power/torque that way. I was initially shy on the valvetrain changes on GT350 and was a bit worried on the spray-bore blocks and the inability to service them beyond their initial bore/hone.
And yes the spray bore oil burning is a no go for me. I thought about having a Gen 1 block sleeved to the 3.70 but it was too cost prohibitive at the time. I never though of the oil cross over on the heads. I've seen the cooling mod like that but never the oil setup until you.
Good Stuff!!