I was going to say 34 - 36 since you just blew a gasket and didn't hear any pinging, but with your low compression 38 is probably fine, although maybe not needed with that cam and make sure you listen for pinging. I run 38 locked in my car but I don't usually recommend it to others because it is on the high side and you probably won't feel the difference but may be able to measure it. Also, that is 36 all in at 3 - 4k rpm and with the vacuum can unplugged, then plug it back in and have fun.
I run two light springs in the dizzy as even the medium ones seem to drag it out too long and aren't all in by 3k, you have a mild converter, so it should be fine with two light springs. You don't want to set it at 3k if the timing keeps climbing above that due to heavy advance springs, or that is a recipe for bad news.
So to sum it up, disconnect vacuum advance, rev it it up while setting the timing until the timing stops climbing, then set to 36 or whatever you decide, then hook the vacuum advance hose back up and you should run pretty good.