First: You need to know the size of the battery tray Length width and available HEIGHT..
Now if the fit: I suggest a pair of GC-2 Golf Car batteries. These are Flooded wet cell (Means you can add distilled water as needed) and they are DEEP CYCLE (means you can talk 'em down to half full before serious damage sets in)
Many RV's come with Group 24 or 27 MARINE/deep cycle, these need to be kept 75-80% full or damage (Shortened overall life) sets in FAST.
Group 24 75 AH each 150 total (Approximate)
Group 27 95 and 190
Group 29 105 and 210
GC-2 220 give or take 10... And Again you can use 50%
4D same as GC 2 if DEEP CYCLE but 2x as heavy as the six volt GC battery
GC-2 is also the most common battery made (lead acid type) and thus the cost of production is lower due to lack of re-tooling every couple days.
Get 'em at Sam's or Costco (Sam's generally lowest cost).
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times