Need new battery

Hey gang, I just acquired a 1257 Wheel Horse. Starts really hard. Pretty sure I will need to rebuild the S/G. I noticed the battery tray is much bigger that on my 857's. There is a piece of 2x4 to fill the space. What size battery should I use. May also replace all the large cables with new ones. Thanks for the help

Nice tractor Bob!

I use the U1LH on those, 275amp (19HP) left hand positive terminal and put it toward the rear. The original battery was a mid size that is getting hard to find and expensive. I've had the best luck out of the O'Reilly Super Start line.