Does the chip in the computer(that can be replaced) control the shift points as well as the 4500 rpm redline?  It seems to me that the engine has at least another 700 to 1000 rpm thats useful.  Oh this is for a 82 crossfire.

And along that same line... any mods that are done will the computer basically limit you to those parameters?

The ECM in the '82 really doesn't control that much. It controls the injectors, of course, the idle speed, and the ignition timing...that's basically it. A new chip(PROM) can be had that will modify the parameters a little, to help with performance, but....you're really limited to what can be done, due to the slooooow processor speed of the ECM in the '82. An aftermarket chip will make the most difference at WOT(wide open throttle), and a little at idle.
A Crossfire really runs out of steam around 4500 anyway, due to the design of the intake...not much you can do about that.

The transmission is not controlled by the ECM, other than the torque converter lock-up. The shifts are controlled mainly by the TV(throttle valve) cable adjustment, and the governor weights and springs. The TV cable is fairly easy to get to(with the air cleaner off), and easy to adjust for later/firmer shifts, or earlier, softer shifts...