Hi Charles,
Thanks for your advice, at least it doesn't limit me to looking for Mustang only part numbers.
I'll make a note to check the other casting numbers, the engine was running but it was only the intake and carby that had been swapped out (2V manifold off a C8zz, and carby C9zz) I do recall my block being a C4xx but the exhaust manifolds were C3xx, I do have Bob's book so I'll check through that as well for the casting dates on the heads.
If you could check those intakes you have I really appreciate it.
Thanks again,
Dom