help! need cb450 head

AARGH. started to build an old seized cb450 engine to 492 cc, got the bottom fixed up, bore is a1.
Took head apart and kept getting this funny feeling.
Looked more closely as I started to clean it after disassembly and AAARRRGH its a 500T casting. :shock:
somebody in the past put the 500t head on the K3 CB450 motor. checked the pistons, yep , bottom is 450 ok.
so I need a 450 head casting, bare or whatever, I have all the rest. Anybody got one, email or pm me to talk please! [email protected]
thank you