318 polytastic!
This is one of the inaccurate rumors about A blocks. A-blocks are the exact same width from outside factory exhaust manifold to outside exhaust manifold as an LA318, so one would have the same exhaust side clearance issues with an LA in a 1967 - 1969 Barracuda only there are far more off-the-shelf LA header options available compared to the A to help deal with clearance issues. I'm not saying an A-block is a bolt-in to a 67-69 Barracuda, but a B/RB certainly won't fit better. The A-block heads protrude out plumb with the exhaust manifolds whereas the LA heads are narrower with the exhaust manifolds sticking out. This diagram dimensions the differences.
This is one of the inaccurate rumors about A blocks. A-blocks are the exact same width from outside factory exhaust manifold to outside exhaust manifold as an LA318, so one would have the same exhaust side clearance issues with an LA in a 1967 - 1969 Barracuda only there are far more off-the-shelf LA header options available compared to the A to help deal with clearance issues. I'm not saying an A-block is a bolt-in to a 67-69 Barracuda, but a B/RB certainly won't fit better. The A-block heads protrude out plumb with the exhaust manifolds whereas the LA heads are narrower with the exhaust manifolds sticking out. This diagram dimensions the differences.