I can only think of three "niche" markets that traditionally go with big block Ford engines.
(352, 390, 427, 428, 429, 460)
* 1960's retro-factory-drag replicas like the Thunderbolt based on Fairlane and Galaxie platforms,
*1967-73 Mustang resto-rodders, and
*Cobra replicas.
Even combined, I think the numbers of guys building their own cars is too small to demand a low-cost supply from the mass-market performance parts manufacturers.