How to repair valve guide boss

he already has anew bronze guide inside the factory one
what RRR said
machine all the factory ones down to the spring seat and run viton seals
what's the od of the new bronze guide
old rubber seals are junk after 25 years even if not run
viton cost about two orders of magnitude than rubber- silicon is just slightly more than buna-n / butyl compared to viton which is the premium stuff