Over the years I've run the zenith, weber 34ich, and Rochester. I've had love hate relationships with all of them. The Weber was the least problematic of the three. I had some issues with Mexican fuel that were easily solved with an additional filter. On long highway hills it always seemed short of breath.
The Rochester will pull my overdrive on hills that required popping back into fourth with the zenith/weber. After installation it takes some fiddling to get just right - when it is right it runs great. Maintenance free with the exception of wiping it off between the carb halfs every now and then. Mine seeps a little fuel and not cleaning from time to time - it gets smelly.
My experience with the zenith hasn't been good. I had one warp two months after purchase and the replacement seemed to run great for a few thousand miles - then need attention. Poor idle etc. The Rochester pulled better on the highway and ultimately I never trusted the zenith after the first one warped. I became obsessed with it - every hiccup I cursed "damn things warped again."
I'am running the rochester now..
Henry