The 4 barrel intake from a 1978 Matador would be for a spread bore Motorcraft 4350. I am very, very familiar with both the intake and the carburetor. I like both of them. But they would be extremely difficult to tune for a smaller-displacement V8 like the 290. Significant re-jetting would be needed, if it was even possible. The 4350 uses a variable jet system that's based on throttle position. It can be tuned a little bit, but it seems to work best for the 360 to 401 cubic inch V8s. Then there is the really daunting task of finding a Motorcraft 4350 that is in decent condition. Those I've seen in the rebuilt boxes are generally on their last legs, and, really, just crap. I found that I had to rebuild them again because the main body had warped over time and I had to file the top flat. Motorcraft made a significant change to the main body between the 1976 and 1977 model years that requires different main body to air horn gaskets. But any more, repair kits only come with the 1977 and up gasket, which will cause a fuel leak onto a hot part of the engine if great care is not taken while assembling the carb. Then AMC used a fibrous insulating gasket about 1/2 inch thick that goes between the 4350 and the intake that is designed to reduce vapor lock and fuel boiling. Those can be hard to find, but some kits have them now.
Edelbrock makes an intake that'll drop in. Believe it or not, the AMC dual-plane 4 barrel intakes actually flow better. That tidbit was given to me by an Edelbrock engineer some years ago. Another possibility might be to find one of the early 4 barrel intakes that'll fit. (Be double certain sure to get the mating surfaces lightly touched up at a machine shop to prevent leaks.) Then find a Weber or a Weber clone and estimate the jets you'll need. A lot of work. If someone on the list has made the swap, I'll go away now, and eat worms in the garden.
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