Anyone contemplating building a Poly should pick up Victory Library's "Chrysler Poly Performance" - I think a member here wrote it but can't recall his name.
It's a great resource & delves into a lot of stuff.
I've had a few - '63, '64 & '65 318s - and they didn't seem very octane-sensitive to me, they'd run on anything. Not sure I'd worry much about improving quench.
Then again, they were stockers, never pushed the CR, just drove them. Decent street motors, and not everything needs to make 600HP.
They used heavier castings than LA is what I've heard, and metal costs money. Chrysler would do anything to save a buck.
It's tempting to think "BBC" when looking at the valve arrangement, but ported Poly heads seem to max out at around 250/200 CFM I/E.
Subtract about 50CFM each side for stock.