I have always assumed that all R/T had sure grips rears. I have a 70 440 R/T that is coded for a 3.23. They have changed the punkin to a 4.10 sure grip but gave me the original 3.23 open set. My broadcast sheet is not coded for a sure grip. I have the sheet for another 440 R/T and it is coded the same 3.23 open rear. I just bought a 69 R/T 440 and it is the same. Is this correct?

A sure-grip was not STANDARD in any musclecar that I can think of.

Some of the "package" cars had a sure grip as part of the OPTIONAL package. "Package" cars include Superbirds, AARs, T/As, 440 a-bodies and others.

I had a friend with an 71 FC7 R/T and it had a 3.23 single leg.

-Daty

Posi was still an option when they built the Buick Grand National, and there is a car that needed it!
My cousin has one he bought new in 87, only has 7k miles now, but when it was new, it would fry that one tire.
As far as I wanted, until he swatted me and yelled "let off!"

Yes it was an option on the mopars too, and not a very expensive one at the time, either.
Of course, back then I was in Vermont, so most of the new stuff ordered at 63436 (dad's dealership) got it.

i worked on a bone stock 440 R/T 69 charger that came from the factory with a single trac 3.23