I've got a 350 with around 9 to 1 compression, Dart 180 Aluminum heads, Edelbrock Performer EPS, 600 Holley, HEI and a Comp solid cam with (I don't remember the exact numbers) somewhere in the 280 degree duration and .512 lift range with 1.5 to 1 roller rockers, I run 12 degrees initial and 36 total timing with the vacuum advance hooked up for constant vacuum so the timing drops when you initially step on the throttle, I have a dedicated vacuum gauge in the car and it idles at 15-16 " cruises at 20-21" and on deceleration I've seen as much as 26", I run it in front of a 4- speed transmission, it's got a really cool choppy idle, great throttle response will spin 6500 rpm in a heartbeat and runs on 87 octane fuel, what's not to Love, every part plays into a combination, I got lucky but I also didn't go too radical with anything as I was shooting for a good tractable street engine which it is and then some, tune your idle air screws to the best vacuum you can get, as much timing as you can without ignition rattle and keep in mind SBC's don't like much over 36 degrees and go for it!! Hope this helps, Later