Sprint cars from the "modern" era that had transverse springs in front as opposed to torsion bars. The racers had long passed the use of Ford axles and everything was custom fabricated. Anywhere from the '50s to the '70s.
I believe that measurement is very close to an old 1932-37 or so BB truck kingpin...as far as the diameter goes, anyway. I have an NOS Oem reamer driver which I believe is that size. Incidentally, unit is for sale for $85 postpaid. Has original box and definately indicates BB application. What I am not 100% sure about is the diameter of the BB trcks, and also whether they were the same as the AA trucks? I have an NORS pins, etc., which I will sell for $85 also.. prs518@live.com for pics.