This web page is useful for comparing battery sizes. Note that Delco batteries are maintenance free same as Optima, but not certain they are as able to withstand periods of nonuse. As you likely know, the Optima is size 34.
http://www.batteryweb.com/acdelcoauto.cfm

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles