The shifter I have is Forte's "1969 Camaro/Firebird" shifter. I pieced my swap together rather than buying a complete kit from a place like Keisler or Classic Chevy.
Here's the factory drawing showing 3 out of 4 possible shifter locations (my shifter is actually slightly forward of the rearmost option). Dimensions in mm:
I don't know the official measurement for my shifter location--I crawled under the car and it appears to be about 18", but I can't say too much about the accuracy of that measurement becase I couldn't get the tape measure close to the shifter in the transmission tunnel.
I also don't know the exact part number for the handle but it is a Hurst handle.