Would I be correct in assuming you have more attachments like a tiller, rotary plow and bedder for the Gravely 2 wheel tractor???
Since you have a 2 wheel mule that can carry other attachments I would save the Gravely as it sounds like it is only losing compression and losing the available torque from that engine by what you describe.
The new gasoline engines have been detuned GGGRRR, HIIISSSSS, SPIT, to make the EPA happy and the only way to eliminate that problem is to put new larger fuel jets in the carburators.
The other thing is the fumes from the new engines are much worse as the engines have been detuned and you will need to install bigger fuel jets and or a catalytic converter to solve that, especially if you use the gravely a lot in the hoop houses.
I hated the honda gx340 engine I had on my Timberwolf TW-5 FC firewood splitter as the fumes made me sick and I only solved that by purchasing and installing a catalytic converter and the only exhaust that came out of the engine was carbon dioxide and water.
If you use the Gravely in your hoop houses the carbon dioxide and water created by a catalytic converter mounted in place of the muffler on it will only help the plants in the hoop houses and you will not have gasoline exhaust fumes to deal with anymore.
If you are intent on retiring the gravely the only other suggestion I would make is to invest in a BCS 853 or Grillo 131 and a BERTA 32 inch 2 stage snow caster.
The Berta 2 stage snow blowers are made for alpine snows and they have been making them for many years and would make quick work of the snow you have and the END OF DRIVEWAY MONSTER.
The BCS or Grillo 2 wheel mules can use many attachments and many of the same attachments. You will need to change the fuel jets to reduce the fumes and let them run better OR install a small catalytic converter and larger jets to get more torque
I would borrow or buy a compression tester and check the compression on the engine, you will need someone to hold the compression gauge as you or someone else pulls the
starter cord if your 2 wheel mule does not have electric start.
Having the engine on your Gravely 2 wheel mule rebuilt will not cost that much and the good engine engine shop will bore out the jug and replace or mill the head, replace the piston, piston
rings, crankshaft, crank shaft wrist bearings, connecting rod, crank shaft seals and rebuild the carburetor for you as well.
If you have electric start on your gravely it would be worth the time to change the starter as well.
If you have the compression checked you will know if the engines piston rings are bypassing or you have a small head gasket leak which is easy to fix.
You may just need repair parts for the Gravely and its engine so have a good repair shop look at the engine for you.
My neighbor had gravely 2 wheel mules to mow and blow snow since 1950?, and she kept using them until she could no longer buy parts for the new one she had in the late 1980's and she switched to a wheel horse lawn tractor as she could no longer buy gravely equipment.
Worse come to worse you can invest in a BSC 2 wheel mule and a 32 inch Berta snow blower and keep the Gravely as a back up machine.
If you want to retire the Gravely I would suggest one thing make a telephone call to Joel at Earth Tools and talk to him as he uses 2 wheel tractors on his truck farm and sells them as well. Every 2 wheel tractor he sells is uncrated and assembled and run on his farm for a few hours to make sure that it runs right and the attachments work correctly before he ships them to the buyer or when they come to pick it up.
EDIT: I am adding more to what I typed yesterday:
If you wander over to youtube you can find lots of videos of vegetable growers in Japan(Nippon) using very large walk behind crawler mounted 2 stage snow blowers to remove snow between their hoop greenhouses. These units can be imported here. But checking with the gentleman in West Virginia about a newer Gravely with more power would be more economical in the short run as you could have the old one and its snow blower repaired as well as it sounds like it just needs new bearings and gears all around too.
As far as the the BCS and Grillo 2 wheel tractors they can be used with a riding sulky or a BCS dump trailer with a seat as well so you can ride on the trailer as you clear snow and also carry a gas can too.
The newer big box store lawn tractors should be avoided like the plague as they are nothing at all like the old Simplicity, Wheel Horse, John Deere or John Deere lawn tractors from the 70's and 80's and early 1990's.
The JDLA115 I have is very poor in quality as the 2 stage snow blower that was built by RAD in Canada is a joke and it costs almost $300.00 to buy replacement V belts for it and IT TAKES FOUR HOURS TO REPLACE THEM.
My semiretired wheel horse 244 hydro is a much better lawn tractor even though it only has 14 horsepower. (the snow plow on it weighs more than the LA115 by itself)
You can purchase the older lawn tractors from folks that rebuild them and they also have single stage snow blowers too. You can find them through the Farm Show Magazine on their CD's.
I am not trying to spend your money I just want you to be an informed consumer of information.