Getting your car to the 12's will be easy. A few things, get some adjustable rear shocks and maybe some new adjustable fronts but you can live with old fronts. Got a small block front torsion bar in the front. you will need to get the front end aligned but hey you will get better wt transfer. Loose the OD 4th gear.

As for the motor, if you are willing to tear in to it. Keep it simple. TM6 or TM7 intake the one for the 440 can not recall now or an M1 intake. It looks like you have a dual plane on there. That needs to go. Also if you are feeling really froggy, go for the MP .509 cam with the 292 duration. That is a good cam at a reasonable price. But like stated above a modern one would not be bad either. Yes the 750 or 850 DP will be a nice step up.