Once a person dares to go into valve work it becomes a very slippery slope.
Then and then only you realize, - NO one should be doing your valves but you.
OOOoooppps
Then you discover 50 deg seats..
https://www.enginelabs.com/features/...s-work-engine/
Now you are not anywhere like anyone else.
http://www.enginebuildermag.com/2008...with-the-flow/
Forget the air filters and all the hype that goes with 5 more horsepower bolt on BS, the SE stage kit crap.
Enter the real world of performance!
Hard seat grinders and valve grinders are pretty available because everyone has switched to fancy cutters.
Souix makes great stuff and parts are still available!
There is nothing wrong with using stones, albeit a little more time-consuming.
I like the polish of stones rather then cutters, My work never leaks with just thumb pressure on valves no springs!
That is as good as it gets !