pertronix upgrade?

[926bill]

Cut open the wiring harness,traced all the wires to figure out where to splice,no big deal. Mounted new flamethrower coil. I took the distributor apart and guess what, the new ignitor mounting plate is1/4 in too big in diameter. I used a 1146a pertronix kit which is for a 470 mercruiser I guess I'll have to pull the distributor to see what I've got. Can't see any numbers on it the way it is. Maybe it's not a delco. Any ideas? Thanks.

BC