I built my cable and got it working last night. I used a ftdi usb to 0.100" header cable because I had a couple of those lying around. I basically made an adapter that goes between the ftdi header and the 4 pin molex programming connector in the cart. I only hooked up 3 wires. The 4th wire isn't needed in my case.
https://www.digikey.com/en/products/...2R-3V3/1836393
I found a few weird quirks with the sw while I was playing around. It seems like you need to run the app as administrator and I don't recall this being mentioned here. Also, if you don't run as admin the ICON logo in the upper right changes to LVTong. I thought that was funny.
Now the fun begins!