Rearend gear selection

I have a 68 Dart with the a 273 engine. The engine has been rebuilt .030 over, Egge pistons, aftermarket rods, cam, performer 4-barrel intake. The original 904 automatic transmission was rebuilt to factory specs. I plan to use 8x18" wheels. The car will be a street/highway/fun. I would appreciate some sound advice on torque converter selection (stock or ?), whether to swap the 7 1/4 rearend for an 8 3/4. I have an A-body 8 3/4 with 742 case. What gear ratio would be appropriate? Open or closed gear? Thanks for your input.