Machine work on 6.0 heads
up to .008" off deck
valve to guide clearance .002" - .0027"
valve recession .013' - .027" prefer .026 - .030"
valve height is 2.225" - 2.230" after milling
try to set @ 2.220" for proper lifter preload
using hardened seats?....Stelite
have only used o-ringed heads on tractor pulling motors
if the heads are properly machined they will last till the new egr cooler goes south...in a van I would completely delete but because California has strict laws then look into
https://www.bulletproofdiesel.com/Articles.asp?ID=369