Then under these circumstances I think I would start at about 8-10 BTDC and see how it acts.
Be careful about listening for preignition after about 2,500 and if it starts doing it back off and look into limiting the total mechanical advance.
BTW, there is no comparison between a 318 and a 408 so don't expect the 318 to come anywhere near it.
Do you know if the distributor has an adjustable vac can on it?
a 3/32 allen wrench inside the vac port on the can.
