I found that a moderately modified 235-261 gives sharper throttle response,especially off idle, when the initial timing is set at around 12-14 crankshaft degrees.You have to limit the mechanical advance to 20 crank degrees by brazing or welding the weight stops ,stock advance springs are ok.This gives a total mechanical advance of about 34 degrees.You can set the timing with a fancy set back timing light if you are using the stock 5 degree timing mark.The vacuum advance may need to be limited to about 2/3 it's normal travel if the engine detonates on part throttle.
You don't need a distributer machine to do this,done carefully on a bench,with a protractor and a pointer rigged to the distributer cam if using points.Using an electronic unit will reqire a distributer machine however.
