There are several problems with the 400 Cleveland; first, not all the '73 400s were cast for the smallblock bellhousing and motormounts. They were only used in passenger cars with the FMX auto tranny. I've personally never seen one, and I've looked. Second, in the early '70s, Ford had a great deal of trouble with block cracking in the 400 engines. Together they add up to a very rare casting. Most Ford-only shops and junkyards never heard of it. IMHO, you'd be better off trying to locate an aluminum Cleavor to open out to 400+ inches.
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