Question about switching to 6 volt batteries

I just went through that quandary myself. The best price I could find on the T105 was $144. Went to two Costcos and asked for 6V batteries in the tire shop - the guy gives me a blank stare and says "the battery rack is over in the corner - I have no idea what's there". Looked on the rack; all they had were 12V batteries. Then I went to Batteries Plus and found the Duracells for $100 each so I ordered 2 of them I'll pick them up tomorrow and swap them out. They spec 215 ah instead of the 225 that Trojan specs, but since we never dry camp those extra 10 ah won't make a difference.

Our original Trojans are now 8 years old so if we get that much life out of the Duracells we'll be happy!