The 427 marine motor is a parts bin engineering job by Ford and Chris Craft. They used the royal 427 cross bolted block of racing fame, a fine cast iron crankshaft, low compression pistons, a low rise torque-prone intake from the 352 and 390 series, a RV truck cam, and generic 352 and 390 cylinder heads. The C7JE head is very little different than most common FE heads found on the 390 motors, and they should be quite plentiful. Here is a very detailed photo documentation of the marine 427 head.
Beware, this is hard core motor-head stuff.
Naturally there are some low volume (high compression) parts out there, but the vast majority of FE motors (352, 390 and 428 series) all use essentially the same generic heads.
Regarding the truck with the 427, I can assure you Ford never built a truck with a 427 but Chevrolet did. If one exists, it's a custom job.