Batteries for JD 4230 diesel.

I getting some new batteries for my JD 4230 and was looking for a little help as far as getting the correct size and cranking amps.  The tractor has already been converted from two 6 volt batteries in series to two 12 volts batteries in parallel, but I can't find the size or amps listed on the batteries I pulled out.  I think the battery size I need is 30H based on what the JD parts website says for the gasoline batteries.  Anyone able to confirm that?  I'm going to stop in at the local parts store during lunch, but want to know as much as possible in case I get the parts guy that doesn't know anything (I'm sure we've all had that fun    ).

Batteries for JD 4230 diesel.