I would start at @ 8 or 10 degrees intial timing (your engine should turn over easy when you try and start it).8 or 10 is with the engine running (at idle) and the vacuum hose off of the distributor.then i would slowly speed up the idle ( checking with your timing light) to @3000 rpm too see (and verify that the weights arent stuck or seized) what your mechanical advance is.Then i would put the hose back on the vacuum advance and check the timing again with the engine above aprox 3000 rpm , this will show you where the total (vacuum and mechanical )timing is at. 36 degrees is pretty safe for total timing advance. This is where an adjustable vacuum advance canister makes a world of difference, cause if you use a factory canister it will probably be much higher. Use this adjustable canister to dial your timing in on the top end. this is a safe start ,your combination could require something different.Its a matter of setting and testing probably more than once. you can also buy different mechanical advance weights to tailor your timing. Its up to you!
P.S. If you are playing with the timing you will notice that in your driveway your engine will love lots of TOTAL timing but this will probably change under load, what ever your total timing ends up being just make sure that under load you dont want to have any pre ignition or pinging , you will destroy your engine if you run it like that for a while!
Good luck , hope i was of some help and hope i didnt scare you off. Its a fairly easy thing to do with a good timing light, and i find it alot of fun!
P.S.S. OH YA I like to have vacuum all the time check that you are hooked up to a port on the carb which will supply you with a good source of vacuum. Just my opinion. Sorry Hot57. All our engine combinations are different and so will be our timing procedures and beleifs of what is right! What works on yours may not work on mine! You wont know until you try.