Hydro Gear 318-0610

I have a Husqvarna GTH26K54T with a 199650, 318=0610 Hydro Gear transaxle. Is there any othe Hydro Gear transaxles that will fit up or do I have to find the exact replacement? I've already rebuilt the entire rear frame on this tractor because of the beating it takes on our ground. I dont want to throw a pile of money at it but I would like to put a new/used transaxle back int.