You need an adjustable vacuum advance canister. summit sells them for the hei.
I would set the total mechanical timing to 38 degrees which in your case would be 25 at idle. Then set the adjustable vacuum advance to add another 10. (48 total).
I would use a piston stop to check tdc. You can make a stop with an old spark plug and a short extension welded to the end of the plug (instead of the electrode).
pull all the plugs and rotate the engine slowly until the #1 piston hits the stop. mark the balancer at the pointer and reverse the engine rotation until the piston hits the stop again. The center point between the 2 stopping positions is TDC.
Last edited by 454C10; 11-15-2010 at 03:04 PM.