Hi Jim,
I have an unknown needle that I got from Peabody, in a big bag of unidentified needles, spray bars, and complete NVA's.
It looked like a typical Fox needle, with two knurled nobs, but a much larger diameter body. My calipers measure thread outer diameter about like you describe.
If interested send me your mail address, and I'll post it in a small bubble envelope, free to you. Don't need it back, as I've no Fox engines larger than a 35.
Bill