Characters and NPCs from Dark Future don't have half the characteristics and abilities as their d20 System counterparts, and this means that converting them is quick and easy but relies a lot on the games master.
As a very rough guide, use the Drive skill of the Dark Future NPC as their d20 System level. You'll have to determine what sorts of classes most characters are, but that should be fairly straightforward - Renegades are redliners, Bikers are marauders, Sanctioned Ops are, well, Sanctioned Ops. The level will provide all the relevant bonuses and saving throws. All other characteristics and feats and the like will have to be rolled as per the normal rules.
This will mean that you won't really get NPCs of higher than 10th level, and the average NPC will be about 2nd or 3rd level, but that shouldn't pose too many problems, especially when you're in vehicle combat.
Any skills (including vehicle skills) that the NPC has from the Dark Future website (with the exception of vehicle and gunner skills) should be multiplied by 3 to get an approximate series of skill ranks for them.
A character with the Gunner skill should be able to choose a number of vehicle weapon feats equal to their skill.
If a character or NPC has more than 3 CON points, then each point should be added as a bonus to their Con characteristic roll.