Welcome Chuck! I have a 1970 Mach 1 too and I'm in the middle of build up my first Cleveland for it. Check it out in the Engine build section.
I havent updated it in a while, but I decided to go with the Blue Thunder intake and Sanderson headers instead of the original cast-iron pieces. Replacing those two parts should lighten up the front end over 25 lbs and add over 50 HP/TQ to the engine.
Whats your setup for car and engine? Also, Post some pic's of your Mach 1.