I have a Lee 12.7:1 high-effort box in my '64 Tempest. From what I understand there is a heavier torsion bar inside the box that gives it that 'high-effort' feel, it takes more movement of the wheel before the power assist kicks in.
I had my box done up by Lee about 15 years ago. I had them replace the internals on a standard '64 power box with the 12.7:1 stuff, plus my pump impeller was fragged so they supplied a pump core. The bill was almost $600.
Steers bitchin' though, the box was worth every penny.
