Vehicle Size Modifier

[Varyon]

Increasing TL will typically either see more efficient versions of the old tech or outright new tech. Looking at Spaceships, your TL 9 utility vehicle that's based on a TL 7 truck might have a TL 8+ internal combustion engine (for x1.25 endurance), a TL 9 fuel cell (which might give longer or shorter endurance, depending on how much fuel the original truck held, but will be cheaper to refuel), or even a TL 9 fusion reactor (for something like 100 years of endurance, assuming it can be miniaturized to that extent). That's not even accounting for things that aren't in Spaceships, like large batteries (as in the Tesla). Better materials will result in either increased DR or reduced weight (each increase in TL is +1 step on the Size and Speed/Range table to DR; if your original truck had DR 5, the TL 9 one would either have DR 10 or the same DR but the frame would weigh half as much, allowing for more cargo/fuel). There may be other technologies incorporated at higher TL's - your TL 9 vehicle will probably have realtime monitoring of tire pressure, crash avoidance systems, cameras for blind spots, and potentially things like automated driving or a built-in HUD with augmented reality (highlighting potholes, vehicles/pedestrians that might unexpectedly get in your way, and other road hazards).

If you just want a quick-and-dirty conversion, I'd say +1 SSR to endurance (so x1.5, x2, x3, x5, etc) per +1 TL, covering both better efficiency and lower frame weight, will probably work. You'll still probably want to figure out what sorts of gadgets it has built in, however.

As for SM, Anthony has the relationship there. As weby notes, there are liable to be much more substantial changes in design than "like this, but bigger," but Anthony's advice should get you good-enough numbers.