Remember, if the OEM tires were bias, and you now have radials, add three pounds to the OEM pressure to maintain the same effect.

My 73 door sticker and owners manual says 20psi for both front and rear.  That was with OEM Firestone 500 GR7015 (equal to 225 70R15 today).  I used to run them a little over that at 22-24psi for better gas milage but the ride was firmer.  I got over 40,000 miles out of my OEM Firestones, and sold the car at 86k with the second set of tires BFGoodrich T/A radials on it.  I plan on getting the Firestone 225 R7015's and running about 25psi.

John

One more thing, 73 was the first year for steel belted radials.  The suspension was tuned for this with 20psi.  When I bought the Vette New in 73, chevolet made a big deal about the advantages of the steel belted radials over the bias ply the 72 and earlier had.

John

 Thanks fellows, yes the door sticker is 20lbs, too low to me. So I try 32 up to 35 lbs see what I like,how she handles and rides.

   Dave