1987 Ford F-250 carburator

The threaded hookup may be for a vacuum line going to the exhausts manifold for heat to make the choke work. If it is you'll have to get some type of shield over the exhaust manifold. To hook tha tup if ther eis no provision for it in the current engine.

You asked about the threaded one on the choke that is for a heat tube as vacuum is drawn through that to make the choke work. See pic, the one arrow is vacuum for the choke and the two arrow is ported vacuum for the dist if that is what you need. The reason tehse didn't have vacuum ports is because on older fords the pcv valve hook up was drilled right into the manifold. So they only needed the two I have pointed out.

I imagine you can find something or just or just put a straight piece between your hose and the one on the carb they have those at auto parts as well as adapters that go on the carb or should have to hook up ahose. But you still need one for the pcv hose. I dont' know why you dont' stick with the holley or rebuild the one you have as the autolite although a decent carb is ssmaller thatn the one you are taking off so you won't have the power you did.