An old line I always use with these small engines & AC. "You can drive the car or run the A/C just not at the same time". But kidding aside these newer AC units don't rob as much power as the old ones did. I have an S-10 pickup with a 4 cyl. Sure it takes some of the power but it still runs down the highway real good. I recently put a Vintage AC in my 56. It has the heat & defrost all in the same package. It is stuffed up in there. You don't have much glove box left. I have a 350 engine in it & you can't feel the difference in power with it on or off.