236/242 should be fine. I run a 246/246 hyd roller in my 512 with the Sniper setup and it works just fine. Having the Hyperspark will allow you to add timing at idle and cruise so that will help a lot.

My cam is just a hair too big for freeway cruising with my 3.23 rear gears so you should be good to go. I have 15 inches of vacuum at idle with my cam so you should have more than that.

My 512 makes 485 at the rear tires which is probably around 550 at the flywheel. Here is a recent article from Hot Rod on my combination: https://www.hotrod.com/articles/holley-hyperspark-install-tune/