I run Rochester 2G's on Mercury manifolds on a couple of my engines. If you mount them backwards, everything falls into place except the manual choke. Since the Mercury's had automatic chokes, I just leave them that way and they work just fine. I have done both the regular and divorced choke types and they both function correctly. The Rochester has larger throttle bores than the Merc manifold, so the manifold needs some modification. I bore mine out all the way down, but "bell-mouthing" the top may be adequate. On a stock, original car, I would have the Holley rebuilt. I use my '51 with a modified Merc engine as my summer daily driver, and for that, you can't beat the Rochester. One of them flows about as much as 2 94's or 97's with no linkage or balancing issues.