Ross,

You could just install an external alternator controller that will allow you to program the alternator to safely charge either your new AGM or future LiFePO4 batteries.  Examples include:
Wakespeed WS500:  http://wakespeed.com/products.html
Balmar MC-624:  https://balmar.net/?product=reguor-mc-624-h



--
Mark McGovern
SM #440 Cara
Deale, MD USA