My hot-street Street Hemi was initially passing some oil through the guides, which we cured with better silicone seals.
Initial carb setup was quite fat, fixed that with some stagger jetting and springs (cam didn't make much vacuum).
MSD6 & electronic distributor were there from the start, but swapping coils from Blaster2 to the Ford F150 improved everything including starting.
Plug life was good after the seals & carb work.
Always seemed to me that the stock valvetrain design, plus the OEM rocker-shaft springs, imparts side-loads to the valves.
Intake design seemed to make for goofy fuel distribution except for WOT.
I always made sure that every drive had some WOT time, just for scientific purposes