[brembo]

I have used quite a few of these adapters on Nascars and American Classics, without exception I have used the 1/32 thichness. This sets the underside of the guide flush with the underside of the chassis for minimum ground clearence, we do this because we race on a smooth wood track. If you are looking to retain the standard ground clearence and are not intending to reduce the front tyre size significantly the 1/16 item would be more suitable but may require a spacer washer on the guide post.
Also note that Sloting Plus Guides fit this adapter/scaly combination really well.
Cheers
brembo