Agree with the 2.76-8-3/4, strange it was not on the tag. 1973 is not my forte but this is the best I can do from the tag-
Y39 special order
F58 heavy service package, rear cross member reinforcement welds
F72 single key package
G11 tinted glass, all
H51 AC & heater
L25 trunk light
R11 AM...