Were you happy with the old set-up? If yes, just replace the original type.
CostCo sells Interstate brand lead/acid 6 volt cells for $83 (would need 2, of course) and 12 volt RV/Marine cells for just a little bit more.
If you want more power storage, you can add cells as desired...this is where things start to get complicated. It's not rocket science, but there are lots of options.
If you do the swap yourself, a good idea is to take a photo of the installed wires to ensure proper install of the new cells.
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV