Chassis or House
Chassis: Remove it to an auto parts store or a "Battery Store" (I went to DEKA) and they will match it..
Specificitions you need to pay attation to are
Size (L-W-H) terminal arrangement (Top or side. plus on right or left) and cold cranking amps (You can go larger but I'd recommend not going smaller).
HOUSE batteries .. I very much favor pairs of GC-2 in series (Golf Car batteries) but.. You can do as above too. IN this case L-W-H, Terminal And as many AMP HOURS as you can get. but a caution on Amp Hours
Wal*Mart rates them at the 1 amp rate (how many hours at one amp draw) so a Group 24 pops over 100 AH.. but a Group 24 is at best 75AH at the C/20 rate..
Make sure you rank them at teh same standard (C/20 is best).