I'm guessing you are looking to make a good solid motor. The split fenton exhaust manifolds or very rare, almost impossible and probably not worth any gains. Well you can split the exhaust if you can weld cast iron also. It sounds good, but not sure it makes it moves down the road any better.
Not much for the flat 6s or the 223, but just thought I'd add.
https://cliffordperformance.net/store
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