I have a 64 chevell that has only 64,000 miles. Should i change out the old suspension, and what is need to fit 18 inch tires? Any help would be greatly apreciated

I would start by replacing all the control-arm bushings, and converting to front disc-brakes, especially if you're going to run big diameter wheels, as they have a lot more rotating mass to try to slow down.

Sway-bars and shocks will do a lot toward improving an old car's handling for normal street/cruising use.

18s will fit, but they may look a little "wrong" for the car if you don't lower it a couple inches.

1 have 17s on mine and it needed no mods to work ,rears are 8" front is 7" although you can run 8" in front too