king kutter tiller and 2305

I was looking at a king kutter II 48" tiller that is on craigslist locally for $1100. My question is, Its going on my 2305(18 pto horse). Tsc says they are rated from 20-35 hp, but I am not sure if that is pto hp or engine hp. My local tsc store recommended the 48'' xb because they have seen the kk II break pto shafts on smaller tractors. Jd's tiller is 47'' and they say the 55'' will work also, so I was wondering why the kk II wouldn't work. Am I missing something here? Any thoughts or recommendations or opinions would be greatly appreciated.

thanks cmoore