The Crower is cut on 112, it certain apps I had it cut on 108 and it made for one torquey beast in a 383. Moparts member Hank 71Coronetcop loved his too.

I wouldn't worry too much about idle low speed with a 426" low deck which is basically what you have. Id run like a 340 or 383 converter if it were mine and I agree getting the distributor curved to about 16-18 initial and 34-36 total makes it even snappier.

Even the old purple shaft .484 cam on 108 spread had plenty of vacuum for street driving.

Cannot go wrong with the Crower though. I'm hoping your OEM 4160 has a secondary metering block and an externally adjustable diaphragm so you can jet up anf you might want to tweak the shooter (a 31 rifle shooter almost always works great) and pump cam.

Should be a fun torque monster of a ride.