There's at least two ways that I know about.
Drill and ream the stock valve guides to a 0.500" ID hole, then press in the 0.502" OD guide of your choice. You could even go to 5/16" or 8mm stems, which would be pretty ordinary and would save you valve weight.

You can also insert bronze liners into your existing guide holes which seems to be pretty widely accepted. You may have to ream the guide first to establish a cylindrical guide, then insert then push a ball of the right size through the guide to expand the liner into the guide. Look at the www.goodson.com catalog to see tools for both of these methods.

R.