Well, I have just switched from 389 to 327 but it's not back from the shop yet so I can't comment.... but I will. I have a '63 Corvan with a 140 with the 110 heads. This could be interesting as I do need to climb some hills but the vehicle is almost never loaded. A big load for me would be less than 500 pounds. I'll post my results after a trial. - Charles