Looking for a Stant/MOPAR radiator cap for my 73 Dart

I had a couple od rad repaired in Joplin Mo shop that has been in business 40 years! the man there said these old rad used a 7 lb cap, he said use that on these 50 year old rads. I did stop at NAPA and found them readily avail for like $7. anyone have an input on these 7 lb caps??????