Despite what some folks are indicating the 19” rad in your car is what it came with from the factory. If your 318 had AC or was ordered with the heavy duty cooling option, it would have had a 22” rad. Also in 1973 the A bodies were available with a 26” rad for the first time. Prior to that all A bodies came with a 19” or 22” rad. The rad core support is different between the 22” and 26” radiators so if you upgrade to the 26” it will require some drilling to your existing core support.
As some other have suggested, get a shroud for your 19” and you’ll probably see an improvement.
