New here - looking for Spicer brownie speedometer gears

I've been lurking for a long time but finally decided to join I have been turning wrenches on my various project cars, trucks and tractors for over 40 years. The current issue is my '65 F-350 dually flatbed.

Some background: I bought this truck in '00 with a tired 360 FE in it (original was 352) and six-lug split-ring wheels that were rusty and not very round. Intact wheels even then were basically non-existent. I ended up putting a '71-74 eight-lug 4.56 rear under it, and a Spicer 5831B brownie. The speedometer gears (3/14) in the brownie were way off for my rear gears and 235/85R16 tires, and the quick fix was a Stewart-Warner adapter (ratio box). Recently I rebuilt the Dana 70 with 4.10 gears and now my speedo is 11% slow.

In the last 25 years, the price of these little boxes has gone WAAAY up, although there is someone here on the HAMB who will re-gear mine for a reasonable price. If I could find the right gears for the brownie, I could eliminate the box entirely.

What I need is (to keep using my existing 1:1.5867 adapter) a 4 tooth drive and 17 tooth driven gear. Or to eliminate the box, a 5 tooth drive and 13 tooth driven. I am having no luck finding the part numbers, let alone the gears themselves. (The 5831 parts manual gives some p/n by manufacturer but no tooth counts).

Can anyone help, or better yet, find some dusty Spicer parts on the back shelf? Thanks!