The solution I found for valve seat recession is TUNGSTEN CARBIDE seats by TUCKER. Ex seats have a Rockwell hardness of 46-52. Thats harder than the FA seats, the Kibblewhite seats and the Nickel Iron seats mentioned in this thread. Intake seats are a bit softer at 40 -45 hard. I have had no problems whatsoever with these seats after 50,000 miles on unleaded fuel. Neither have I seen any seat recession problem with the non-symmetrical cam profiles I use.
Tuckers phone number is 800.362.7321 Note that their standard fractional sizes actually measure .005" larger than the fraction. You'll probable have to order in custom sizes (see sizing below).
Custom order for stock seat replacements:
Stock EX seat is .250” tall, seat recess is 1.5 (use 1.507 OD seat – custom OD). ID is approx 1.185 x .159” wall, ask for 1/32 wide seat mating.
Stock IN seat is .250” tall, seat OD approx 1.557”. ID tapers 1.312” to 1.4” x .128” wall, ask for 1/32 wide seat mating.
Use .007" interference fit into valve seat recess. Cut seats with New Way carbide valve seat cutters.
You can use high quality harder seats or softer seats with a shorter lifespan - the choice is yours.