FWIW, mine sounds just as good, stock 73 318 bottom end and heads (never touched since 73) ld4b intake, edelbrock 600cfm carb, 340 cam, and headers. Goes pretty good but still not that fast, I'm guessing low 15's high 14s with 3.23 gears and 275/60/15 tires in the 1/4.
Higher comp, bigger cam and better gears and id think you would get low to mid 14s.