BB Duster w/factory manifolds

74Duster,
The 400 is narrower than the 413-440 engines by about 2". I used a set of B body hedders and had to move one tube and dent the 2 tubes that fit around the torsion bars and had a set of under chassis hedders, that fit and worked. The tube that had to be moved was the #6 cylinder tube as it would have hit the fire wall and I just twisted it to fit in the area behind the shock tower, made a slip fit on the bottom and welded a tab on the tube that I moved and to the stub of the hedder that was left. It made it real easy to change plugs too as it took all of a minute to remove.