You don't need to modify the dizzy casting to install in an A-series. Fits in just fine.

Limit of ANTI-clockwise rotation (this photo):


Limit of clockwise rotation:


There is plenty of room in a 1200 for any position in-between.

If you try to line up the cast-in hold-down bracket, the vacuum advance hits the block:


You could create a Chevy-style "fork" hold-down bracket to secure the E15 dizzy.

Or you can drill, grind, cut and otherwise modify the E15 dizzy casting. See E15 Electronic Distributor Swap