Sent an intake manifold and yfa feedback type carburator for an efi to carburator conversion. Bolts on the intake manifold too narrow for carburator to fit.
I thought all intake manifolds the same. It has the firing order cast on the intake manifold for the inline 6. Do I have the wrong intake

 

Wrong intake or wrong carb. But I am not up on the 300 sixes too much. I think fate is in your favor though, I would not install a feedback carb on a engine with no computer. How is it going to work correctly? You are going to swap distributors too? If so, you are not going with a feedback setup are you? I would get the whole setup from a 82 or earlier six. Carb, intake manifold, distributor, the whole shooting match that works together.

 

Carb is probably a CAR YFA. The ford 250 had a similar carb. Will not work on a truck manifold.

 

Some of the big six intakes had a smaller bolt pattern, the same as the smaller sixes. I haven't figured out if it's a 240 thing or if it's a van thing. The couple I've come across were in vans but I don't know if they were 240's or 300's.

 

I think around the late 70s they changed to a larger carb base. My best guess is between 1976 and 1979 since I found a 79 carb too wide to bolt to a 76 intake once. The feedback carb is the last thing you want to start fiddling with and trying to make work. The whole engine management system was clunky at best when new.

 

On the later 300/4.9L sixes, the two hold down bolts are farther apart, but an earlier carburetor can easily be modified using the later gasket as a template and a small rat tail file. It can be done in ~ 15 minutes. Many rebuilt carburetors come with elongated hold-down holes so they can fit either manifold.