I thought about opening up the speedo on my Hijet, and painting on hash marks for important speeds: 25, 35, 45, 65. As an interim measure I made a label with my label printer, had the kph which corresponded to the critical speeds in mph, and put it just below the speedo, and one at the top of the windshield. Then I found an inexpensive gps Speedo, with heads up display, and went that route
I saw where someone on FB was making a decal with the mph speeds called out on it that you then applied over the speedo as an overlay. Pretty slick. I was just going to use a yellow grease pen to do mine LOL.
I once took a Canadian 240 KPH speedo to The Clock Doc abd he converted it to read MPH, accurately. Would love to do that with my ACTY, but that guy is long gone. there was once gearboxes that made the conversion and fis on one end of the speedo cable.