interesting task. Had a frustrating time when pulling pushrod tubes up they kept pulling the seals out of the crankcase even though i'd lubed the inside and not the outside of the seal.
when i measured the hole i thought the seals i had were oversized (two different types) decided to go and source some more 'oversize ones' and fit noting to that the brand spanking new stainless flash varied in od by as much as 5 thou.
hole size 15/16th seal size 1 inch
new seals put in exactly the same way stayed put when i moved the tubes up after head on...
BTW tube seals are the correct type it seems, where the inner lip is not quite as long as the outer.
thanks Dave (passenger0_0) goes to show that us kiwis are a bit fussier than the 'others'