EVWest has a lot of mixed reviews. I have an OBDII SUV that I converted using a lowish power motor. You are right gearing is key. OBDII by itself doesn't pose any problems but once you get into the mid-2000s and newer, the vehicle CANBUS can get in the way.
Older cars are simpler in many ways so that's why they could be steering you in that direction.
Older cars are simpler in many ways so that's why they could be steering you in that direction.