1. should i be using premium fuel b/c of the higher octane?
2. if i stick to mid grade could i just dump some 104 octane boost and some lead substitute and be ok?

Octane has everything to do with what the timing is set at and what type of pulg you are using. You can run 93 octane but you should advance the timing for it. With gas prices the way they are I would only do this if its a "part time car". Let me know. I can walk you through it.

how would i advance the timing on the old 350?

the hold down bolt on the distributor. back it off till it loose, not off. You will need a timing light.(inductive) not conductive, they suck.) clockwise turn of the distributor is retarding the timing. Counter clockwise is advance. There is a special tool for the distributor bolt, it should be a 9/16's. Most of the time I can get to it with a comb 9/16's. Thinking back now, I had a 73 MC, I remember using the open end to mess with it.

Find out what the timing is set at and write it down. Next, I do it old skol. Which is to fill the tank with the fuel I am going use and start bumping the timing 2 degrees at a time and drive to find what works best. You will want to keep it from "pinging" which is not good. As long as you are doing all that, I would get a after market coil, cap and hi-pro wires, and new pulgs. I would keep a note pad and write everything down along with the mileage. Its makes a good tool...

BTW-timing on all chevy engines you put the timing pick up on the number one spark pulg wire. That is driver side front. All drive side is odd numbers and the pass side is even.

The firing order is 18436572.

8-----7
6-----5
4-----3
2-----1
Like that^^.
Let me know...
tex

ill see if i can do that