I don't think higher octane should be necessary; the stock rated compression of my 318 was 8.7:1, so with the 302 heads I doubt it's over 9:1. This shouldn't require premium gas, especially with my thinner air. I'm going to check the timing first and if it doesn't need to be changed I think I'll just take it easy on the gas pedal until I get dual exhaust.
There was a thread a while back about headers that quoted an article from Mopar Muscle. In the article they found that on a mild engine, such as a 300-hp 360, there was only about 13 more HP found going from "restrictive" stock 318 2-bbl. exhaust manifolds to Hooker Comp headers. At this HP level it's not really worth the expense and hours of frustration for installation.