Thanks for all the replies everyone.

The motor was never overheated so the heads weren't milled to correct any warping therefore shimming the cam towers shouldn't be needed.

I guess what I was really asking was if anyone had insight as to how necessary the shims are for the compensators, I certainly fully understand the theory behind the shims but often practically speaking things are different.

The dealer is recommending doing the whole motor to save having to go back in but as the noisy lifters are all on one side I was thinking about just doing one side.

Cheers
Matt.