76' Ford F100 6cyl runs bad @ high speed

My 76 Ford idles perfect after installing a brand new Autolite carb but when I get it going around 55 or 60 mph and level out it runs unevenly,not a dead skip or anything like that, just uneven, but while accelerating it runs great. Have already changed the fuel filter and installed new spark plugs and wires and dist. cap and replaced all vacumn hoses. Any ideas ? HELP!!

I didn't know you could put a Ford straight six in a Chevy Astro.....................
I think you have a carburetion problem.
Is your carb a 2bbl or 4bbl? Which model?

You either have a lean surge in the primary main jet or (depending on the model) the air doors for the secondaries are opening prematurely.

Some Autolites have an adjustment on the secondary air doors so they will not open too soon.

I didn't know you could put a Ford straight six in a Chevy Astro.....................
I think you have a carburetion problem.
Is your carb a 2bbl or 4bbl? Which model?

You either have a lean surge in the primary main jet or (depending on the model) the air doors for the secondaries are opening prematurely.

Some Autolites have an adjustment on the secondary air doors so they will not open too soon.
Sorry the Ford inline six is not in my Astro its in my f100 truck my astro has a 4.3 ltr v6 in it . The Autolite carb made by Carter is a 1bbl and its new not rebuilt.
model # on the little ID tag is D5TZ9510 and theres another # below it.
AG G2B14 and also theres a # stamped on the bottom where it bolts to the intake 7051SA. THANKS FOR YOUR REPLY,
RAYDIOED

A suggestion, provided that the carb is jetted right for your engine. A vacuum leak? Open throttle has less vacuum than part throttel, a leak would lean it out, and maybe you've adjusted the idle mixture to compensant?
Maybe try finding a vacuum leak with some carb cleaner. Spray around, and the idle will raise where it leaks