Take the mintest head you can find .
Tapering from 32 down the throat to 30 , can , amoust other things , be beneficial .
The Stok intakes are somewhat curved , creating a kink , almost . In the induction .
Whatever , set up carefully , the olde 40 thou of coilbound at TDC being ascetaied .
THEN , a hot cam the hights differant for the same issue . Whatever - Quality valve springs are adviseable .
Any recessing / pocketing in the valve seats means shadowed lift and efficiency lost .
So a good original head with NEW lead free valve seats , high n proud .
Would be way better value than a used head with sunken seats .
The back face ( stem side ) should be flush with the chamber face .
Plenty of people have paid plenty of money to monkeys for ruining there slightly worn but unwrecked heads .
So a low time replacement , or expert competant engineering are in order . Norvil Springs were W&S , same as Johnson Motors TRiumph
from back when Noah was a boy and Triumph held the L S R for 15 years or so .
ARGHH ! POLISHING the snot out of the Cam Follower faces ,
perhaps just REFACING them, ( oil retention )
and mirror polishing Cam Lobes , will help life there too . And Spacers not Thackery Springs on the Rocker Shafts .