the spring tension & or the amt of mechanical adv(slot length) would be different between the two. If 20 gave you 37(& no ping ) I would bump the initial up a degree & if the total is 38( which is a good baseline for a BB) & stay there & play with some lighter springs if you wanted the curve in quicker. EDIT your snap on(w dial back) light is good. the fluctuating marks at higher rpm is either the tchain and or needs one of these on the end of the dist shaft to keep the dist tang from moving back & forth in the slot in the top of the intermediate shaft. check how much play yours has by grabbing the rotor & moving the shaft back & forth, not enough to move the weights out against the springs but enough to see how much slop there is where the tang sets onto the slot.