360 question

Throttle body (TBI) is a type of fuel injection, not as good as multi-port (MPFI), but better than a carburetor for driveability and fuel economy. If you plan a street car, the existing computer should be fine. If it moved a truck, it will sure move your light car fast. One downside of your setup is the heavy cast-iron intake. If you want to be able to tune the TBI, look at controllers from Howell Engineering, Megasquirt, or Holley Commander 950. As mentioned, you would need an external electric fuel pump and return line to get ~20 psi. Several posts on that.

If you want a more performance cam, but retain low rpm driveability and not drive your computer crazy, look at Rhoads leak-down lifters. Not sure if they made a roller lifter version. I expect you could retrofit any SB cam & lifters, even mechanical lifters with rocker arms from a 273.

Your auto trans probably has a lock-up torque converter, which is good for highway mileage. If a 904, it probably fits your tunnel, a 727 requires beating the sheet metal lip flat. If an overdrive (4 speed), you probably must cut the tranny tunnel and re-weld plate. At least people who install a Magnum engine & tranny must.