I'm about to start an
Autoduel campaign as well. I'm not going to bother converting
CW>
GURPS, though; mostly planning to use it as is. For vehicle combat, I'm currently debating whether to keep
CW to-hits+skills or use
GURPS skill rolls—I haven't decided yet. Damage to vehicles can stay with
CW for the most part; conversion is only necessary for
personal effects, in which case it will probably use the
Occupants Hit stuff or find an equivalent weapon as appropriate.
But yes—you will definitely need
Ultra-Tech.
The
Autoduel Atlases had some
GURPS versions of
CW vehicles which can be used as a guide if you're going to attempt a conversion, you'd just then have to convert to 4e a bit.
Here's the
wiki (very WIP at the moment)