Adding DI input to Ampex AG440

[Cosmonaut]

Hi everyone, I'm selling my Ampex modified preamp, and a guy asked me about putting a Hi-Z input and phantom, I don't have any clue about adding pantom, but not sure about how would be the easiest way to add a Hi-Z input to this preamp?

I thought about the JLM kits...but being in spain it would be to much time waiting for the modules, etc...

Anyone know a better way with this module for adding this?