Picking up an old Bracket car. Have some questions

The 1st thing I would do is pull the transmission (assuming it's a 727) and go through it completely. Install A@A's best sprag and steel front drum and a good shield.
Next, go through the brake system completely.
Make sure your steering components are tight and in good shape.
You can get a new harness pretty cheap, we all have to get new ones every 2 years, it's the nature of the beast.
Also, you can get a battery hold down pretty cheap, and it doesn't need to be welded in you can just bolt it to the trunk, but I think you have to use 3/8 or bigger bolts.
Check all of the wiring for missing/chewed on insulation. Depending on where it's been sitting for all these years you could have some issues there.
Enjoy your bracket car, they are fun!