Welcome to CHR Nate. IMO the quickest way to go fast is a lot of cubes in a light car.... Might want to consider a stroker engine, maybe a 496 or it your budget allows a crate engine 502. Hook it up to a well built street/strip 400 hydro and go have fun!!!

As for the rear, not sure on the '73 how much bigger a tire you can run... You could go with some mini-tubs, 3" or 4" wider then stock, this would allow at least a 10" wide tire on the rear.... Again, back to your budget on just how carried away you want to get....

What rear end is in the car? I've seen 10 bolts survive quite well behind a BBC, a 12 bolt or a Ford 9" would be better though.... The 3.73's are a good ratio for the street, good low end and still affords decent rpm at cruise speed.