Personally id have put a bit of Sikaflex to seal around those wires, just to make sure no water can enter the cab.
In my car audio install days, i always ran any wires through firewalls so the wire went "up-hill" just before the firewall, this way any water that collects and runs down the wires, will always run away from the rubber gromet instead of feeding water into it.
I used a coat hanger cut down and straightened, and hooked the end of the power cable (which had a fitting for the battery already soldered and clamped on) and just pushed the big grommet near the accelerator, the coast hanger pierced a small hold and went through, then fron the engine bay I pulled the end of the wire through (tight as). Hole is smaller than the wire and tight fit. Mostly water/dust proof I'd say. Took about 2 mins.