Take a look at Earl's. I had a problem with my GT40 heads and the interface with Sanderson headers and had tried several other brands for fit up. I also had to use Breslin header bolts, again because of the headers. Even ARP studs wouldn't fit. Reasonably priced tho not cheap
Below is the Earl's description - you just replace the insert rather than the entire gasket assembly.
"Pressure Master Header Seal, for Ford 289–302–351W (Except Boss), Pair – Designed and manufactured for Earl's by Parker–Hannifin Corporation, these seals are the first High Performance Seals developed to solve automotive sealing problems using Aerospace Technology.
Pressure Master Header Seal, for Ford 289–302–351W (Except Boss),
The graphite foil sealing inserts can be replaced in the aluminum retainer, making it an economical solution to tough sealing problems. Replace the seals on a smooth flat surface using even pressure for best results.
Uses Aerospace Technology
Graphite Foil Sealing Inserts
Seals Up To 1200% Better
Superior Torque Retention
Longer Lasting Pre-Load
90% Break Loose Torque"