Where should I start?

These guys have already given you some good suggestions and I'm glad you're gonna put the 8.75 rearend in it with the 275/60/15 tires and run the car as it is after that for a baseline. I run that tire on my Duster on an 8" wheel with 4.5" backspacing.

Small blocks really like a lot of gearing, your motor would probably like a 4.10 but it will be miserable driving 70 miles to the track with anything over your current 3.23, a 3.73 ratio is the highest I would go in something that gets driven a lot but that's only my opinion.
An A-500 overdrive trans will bolt right up to your motor, but might require some dents in the floor and different trans crossmember, I'm not real sure on that but it would be way cheaper than any other overdrive setup.

A 'Good' converter makes a huge difference in a car with a stock type converter. Get some affordable shocks and go from there. You can always add stuff as money allows, such as heads, headers, intake, carb etc. Free flowing exhaust, or cutouts, will also help.