Thanks. Given the 105 Ah, I just assumed Group 31s. Useful to know yours are narrower...
I've been eyeballing the space where my starboard bank lives -- 3x Group 31s -- in peaceful coexistence with my genset battery (1x Group 34), and 4x 6V deep cycles will fit there without displacing the genset battery. That would increase that bank from 300 Ah to about 450 Ah... and maybe more if I have enough clearance to use the slightly taller 6Vs.
I also confirmed that new 6V bank would still supply enough CCAs to start that engine...
Don't actually need to do anything until that bank goes south, but we're starting our 9th season on 'em... so I've been shopping for battery boxes, too
-Chris