There is an outfit in Eatonville that has lots of used parts, mostly mustang but I got a flywheel there that fit my '65 289 C-4 auto just fine:
Mustang Ranch
36210 108th Avenue Ct E
Eatonville, WA 98328
(253) 847-2623

Also Ron Boesl @
Northwest Classic Falcons
137 NE 109th Ave.
Portland, Or.
503-241-9454

Good luck
Jerry