I have a 68 fury so I'm biased, my thoughts:

Some of the earlier C's are not a lot heavier than the later B's

The C's can take almost any wheel at the back you like, the front gets interesting though.

A stroked SB with a 518 auto would be a better option, the combination is lighter and cheaper if you want the overdrive

Some Aero mods like a belly pan would pay off pretty quick on frequent commutes

You need to go to a really big 4 pot or 6 pot caliper to exceed the surface area of the single piston on the 69 and later C calipers, they are heavy, but they work fine

Do you guys run cars on propane much over there? no one seems to mention it, but its not uncommon on traditionally heavy fuel guzzlers here in OZ