Moving to the doghouse cooler, you may not have known this, but VW used four types if grommets for their oil coolers: Early Beetles and Buses; Type III to 1969; 1970 and later for all types, especially doghouse coolers for 1970-'79 Beetles and 1970-'71 Buses; and tapered grommets used to adapt new 10mm coolers with old 8mm cases (changed in 1970). These are installed without using any kind of sealer as not to clog the oil cooler.