OK, Mike and I have let this thread run out a couple of pages and think there are a couple of things to think about not yet discussed.
The op states that they want to run XXO/Prod this season but then cites Vintage Category rules concerning allowable ignition mods. There are NO Vintage Production Coupe classes so these restrictions do not apply. Section 5.B.4, last paragraph on page 78 tells us that a car considered as production will run in the /VGC classes.
This leads us to page 90, section 5.E Production Category. The car would be legal in the XXO/Prod class if the top has NOT been chopped. If legal, body wise, any ignition is now OK to use.
Problem solved. Questions?
DW