if you think about it, orig was just rubber, now days viton, teflon, PTE rubber, synthetic, and metal/ teflon,
so many choices, but, most are running their cars alot harder than we used to, so heat is a factor,
along with HD oil pumps (more oil up top)
I use a teflon/metal, but thats just personal choice,
BUT....... what ever you choose .. IT MUST CLEAR THE VALVE RETAINER, AT FULL OPEN,
most need to have the guides cut, both OD, and shorter.