I've used a CETEK smart charger for years on all my batteries, regular and AGM, including my very expensive classic battery in my 67, works fine. It has a separate setting for AGM as well as a "reconditioning " mode.
CTEK - 40-206 MXS 5.0 Fully Automatic 4.3 amp Battery Charger and Maintainer 12V https://a.co/d/9DvsPNJ
CTEK - 40-206 MXS 5.0 Fully Automatic 4.3 amp Battery Charger and Maintainer 12V https://a.co/d/9DvsPNJ