magnum matched to 904

I dont aprove of slotting the holes in the flex plate. I know, its not my call but
I've seen flexplates and flywheels (GM) that were run for more than a few days with loose torque converter bolts. Result is oval or egg shaped holes. The bolts will never stay tight again.
If I couldn't come up with a correct fit I would fill and redrill the holes on size.
Just my 2 cents Good luck with it.