What Pete said. I do have a 4 down to 2 adapter that will work on a 305e and should work on a 351M manifold, but the results are rather a waist of time. I tried it and felt a little difference, but had I cleaned and rebuilt the 2 barrel it probably would have been the same. haha Not until I got a manifold and actually opened up the plenum did I notice much. But that's with a 4 barrel....two barrel doesn't really Need a manifold mod. Like said, if you do a 500 best to get an adapter and put it on. The 500 mod is the most common...I think 3/4 of the v6's here have it!
