It is about 4.25" in lenght. The one you have might be the top bolt. There are four bolts on the plate. The top two are about 3.75" in lenght and the bottom two are 4.25". The bottom ones are longer because the steering linkage attaches at that point to the back side of the front wheel supports.
I'll keep looking as I can't put the left front wheel back on until I find one that matches. I'm headed out to Suffolk Virginia in the morning to search a few junkyards. Wish me luck!
