I snagged some Sears Plus Start batteries on sale for $59. I have also bought used from an auto salvage yard for $25. I think the size is group 24F. Take your measurements and note the orientation for + and - posts based on the cables. I keep unused batteries indoors over the winter and rotate a HF battery float charger between them with 1 month on each battery since I have 6 batteries to maintain.
I get mine at fleet farm for 21..99 and on sale for 16.00... the usually last me 6 years
it is the 12 L size and although smaller they put out 300 cranking amps...they work great for me...if you are going to use them for an electric pto clutch then you want the higher output or your electric clutch will not engage...
The NAPA book said to use 26R, which is what I got. I measured the 24F, and it might have squeezed into the battery tray, but it also may have been about 1/8" too wide, and I didn't want to risk it.
After sitting in a garage for at least 25 years, it fired right up. It does, however, leak gas out the bottom of the carburetor, so I will be starting a new thread to ask for advice about this problem.