I've got a 750 speed demon on the 55. In my opinion, they are the best out there. I ran a 750 holley which worked good but if parked for more than 2 weeks, it would run like crap and I got tired of beating on it with a screwdriver handle. After that, ran a 750 edelbrock which was alot more kind after long periods of unuse but killed the power. Finally went to the speed demon and woke it up. Great throttle response, the fuel mileage actually went up slightly from the edelbrock, and works just as good if left parked for a long period of time. I love it. It works great, looks great.