[FWB]

it really depends on the particular build you have, there isn't a magic number.
i personally with my build don't pay much attention to my initial, i don't have a vacuum advance though. i run 36 total for street driving with 93 octane exxon and octane supreme 130 lead additive. when i go to the track i run 38 total and 110 leaded racing fuel. i have found with several builds that the stroked big blocks run best at 38 or under, a stroked motor generally speaking is using its torque curve and not high revs to achieve performance, thus not a lot of timing. where a standard stroke might be happier at 40 total, that is if you have the fuel to keep the detonation down. you will have to experiment yourself with your motor and keep a keen ear out for pinging. read your plugs, that will tell you where the timing is right