What MPH are you running vs with the other engine? Different engine combo may require different gears and/or converter. Any major exhaust differences between the dyno and on the car? Restrictions? With the carb, accelerator pump squirter size & duration mostly influences 60' while jetting mostly affects MPH. Any carb differences between engines? New engine may be more sensitive and/or needs adjustments to vacuum secondaries if they are opening too slow or too quick. FWIW, in my experience, a properly tuned mechanical secondary carb will outperform a same-sized vacuum secondary carb by about a tenth. But a vacuum tends to be more "drivable" on the street.
Last time I ran the car with the old combination, I had valve float issues and couldn't rev the car past 5400-5500 rpm. In the past, before the valve float issue, the car ran best being shifted around 5900. On that day, with the same carb but, a different intake, the car ran 107.5 mph, today, it ran 104mph on the best run.
It is a mechanical secondary carb. The AFR is pretty good everywhere, per the wideband. Maybe it can be better but, not 130HP better, we're talking probably 5-10HP if I really got some seat time in it and tested and changed things and tested some more.
