Mark;
If you don't mind paying for the race gas, there's no reason you can't leave the 12-1's in there. I would swap out that cam though. I've ran the non-nitrous version of the same cam on the street and it's pretty rough on valvesprings, not to mention the potential for roller lifter failure in a predominantly low rpm street gig. (don't ask me how I know that
)
Stepping down to a smaller roller will only sacrifice a little power but reliability will increase dramatically. You could also swap to a flat tappet solid cam...once you've cleared the break-in hurdle, chances are you'll never have to worry about it again. Obviously a flat tappet cam will require different springs, etc., but you can always sell off the roller parts to help finance the swap.
The 3500 converter and 3.73's should work fine with the right cam choice, but whatever you do, don't buy 1 of those "off the shelf" speed shop special converters, pay the money for a good Coan, Art Carr, ATI, BTE, etc. You'll be glad you did. Your motor should still be capable of wasting a generic converter with anything resembling decent traction, hence my recommendation for a good converter.
As far as the Dominator goes, you can clean them up to behave pretty well on the street, but gas mileage is never going to be a strong point. Dominators do peg the "wow meter" when the hood's popped at the car shows though.
Which model do you have?
Just so you know where I'm coming from, I was an engine builder/machinist before I went into my current business.
If you'd like any help with cam choice feel free to ask. I'll be glad to help.
Eric