My 1968 look very similar looking to this with a galvanize finish I think. I'm guessing at the size .Hopefully someone knows. I think 72 is the same. McMaster-Carr
If I had to guess I would guess they were #8 originally but yes these are the correct style for a '72 as well. Likely 3/8" of an inch long but these cars had some very esoteric length screw here and there.
