[bwdbrn1]

I tried poking around on the Sears site, but couldn't come up with an answer for you.
Here's the owner's manual for that tractor, if you didn't get it with the tractor.

http://www.managemylife.com/mmh/lis_pdf/OWNM/1008359L.pdf

It says the snow thrower attachment cuts a 40" swath, which is what the 842.240722 is.

"SNOWTHROWER has 40-inch swath. Drum-type augerhandles
powdery and wet/heavy snow. Mounts easily with simple pin
arrangemenL Discharge chute adjusts from tractor seat. 6-Inch
diameter spout discharges snow 10 to 50 feet° Lift controlled at
tractor seat. (Use with chains and wheel weights and/or rear
drawbarweighL)"

So that's promising. Couldn't find a manual for the snowthrower though, sorry.

 

[bwdbrn1]

For what it's worth, I went to the Chat Line one the Sears Parts site, and here's what I got out of that.

"Please wait for a Sears Customer Service Representative to respond. This chat may be monitored or recorded for quality assurance purposes. Your average wait is 4 seconds. Thank you for holding.
You are now chatting with Brian D. How may I help you?
You: Hi Brian, I have a question about an older garden tractor and snow blower, if they will work together.
You: the tractor is model # 917.255980, and the snowblower is model # 842.240722
You: Opps, my name is Bruce W.
Brian D: Bruce the snowblower is a 40" and the mower deck is a 44" they will not fit.
You: Thanks, is there a place where I can readily find the models of snowblowers that will fit the 917.255980?
Brian D: I recommend visiting Sears.com or call 800-349-4358.
You: Thanks Brian, I'll try that."