Engine options for Troybilt 42" tractor, Model 13AJ609G766 ???

[Grandpop Bubbles]

I blew a piston on my spare tractor, a Traybilt Model 13AJ609G766. I would like to repair it because I like the hydrostatic trans, but Ido not want to spend $700 for a new engine. Since I haven't found a cheaper, used short block or engine, I am wondering how to figure out if any other engines would work in it. Thankfully, my Craftsman 42" is working, so -- other than my wife "suggesting" that I get rid of it -- I am in no hurry. My current engine is 31P777-0293-E2. Thanks.

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[WranglerX]

Might all depend basically on shaft size and diameter and diameter of bolt circle to mount it.. What engine is on it now?....
Might be something out there like I did for my log splitter, it came used with badly broken B&S 5hp engine, I could have spent $350 for a new brigs or $375 for a Honda, but chose to go with 6.5 horse Predator from Harbor Freight for $139.... And it bolted up right up because it has all mount for base and hydraulic pump correct... And if it puke it guts out I can replace it easily and still be off less investment the new B&S or Honda....Only negative, sends money to China...