You could probably get away with using an 8 1/4 for a while but definately upgrade to an 8 3/4 or 9 1/4.
If your set on a 440 and you have a good one I definatly would use it that low rpm torque you get out of big cubic inches is tuff to beat.
I have a 77 Ramcharger that I have a very mild 500 cubed big block with 3.23 gears and its a total blast to drive around town, no loose sloppy convertor and idles great sitting in traffic.
Yours sounds like fun, mine has the unleaded valves and runs on regular gas, came in my 64 Savoy race car and ran 7.77 best, of course it had good vert, 509 cam and 4.88 Dana, big tires all steel. Pulled it for a better 440 and been sitting there waiting.
