340 No low end power

Loose the intake. Is the carb an aftermarket carter or an old factory avs ? I would swap the car for a new Edelbrock AVS 650 so you can get tuning parts easier.

The unilite will probably burn out at some point and when it does replacement parts are almost as much as a new distributor. but for now you need to find your total timing also. You may have 13 initial and to much total.

How much vacuum does it have at idle ? is the idle rough or smooth and what rpm does it idle at. Im betting its got a 284-.484" Purple shaft in it which is why it doesnt feel very torque. That cam and 3.21 gears with a stock converter is going to feel like a slug.

Pull the cover off the rear and see what the ring gear is stamped with. Im betting 2.76 or 3.21s