I'm replacing the input shaft bearing retainer.

I removed the old retainer, pulled the bearing race and shim. I put the race only into the new retainer and measured runout using an Amazon vice grip/flex shaft dial indicator.

I measured .037". I have .038 and a few other shims.

My question is, how close to .037" do I need to get?

I also have decent confidence in the Amazon tool, but if there is error it will be with shaft flex that will result in undermeasuring the runout. I may loose a .001 or two of measured runout to shaft flex.

My first time doing the job.

I did find an excellent series on T5 rebuilding on YT by JunkYardDog where he put in exactly the amount of shim that he measured.