You're talking about the early ones, right?
I haven't had to attempt that yet. LOL.
Do you have the special tool to press out the diodes?
I've got two 'single field' alternators that died, and an isolated field roundback I got at a junkyard when one of those roundbacks seized up. The junkyard alternator has been a reliable backup. LOL.
To my surprise, all the diodes tested good in the pre-70 roundbacks good but the rotors in both had open windings.