GPS is a nice thing to have to test speedo readings. A good AP to have on your phone. And yes, when I changed over to 3:55 gearing in back, I had to get an adapter. Different tire sizes affect the adapter.

Craig

My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear
My truck ....... Respect The Rust
If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.