I run 2.76 in my 77 van with a 318/727.... runs great and milage is great also!
318 is out of a 76 duster and has only 52,000 miles, I put a double roller in, ld4b intake with a holley 450 and a set of hooker headers and rear is a 741 with an old style sure grip.
I think with a 340 in ur dart...