Hy jmh, you could contact your local Napa or whoever your local nationaly affiliated auto parts supplier is, or if you have a truck repair shop in your area you could call them and ask them who they would suggest. On one of my 46s low speed is to the right on the dash control, but that is a different style of controller than a 48 would use, seeing as how you need vacuum to shift into high range you should always park in low.
