I currently have a BAK X4TS Revolver installed. Fitment was an issue from day one. The cover itself was manufactured too long placing the plastic tie down clips against the back of the cab. The T-Slot rails BARELY overlap on to the top of the bed, hanging on the radius edge causing it to leak...
You could always use a tone generator and Probe. Disconnect the battery and connect the tone generator to your desired device’s terminals or wires. Go to the fuse block with the probe and start touching each fuse. Klein makes a relatively inexpensive one, I’m sure Fluke makes a very good albeit...