Removing that stumpjumper with all remaining intact will be almost impossible.
I've used a hydraulic puller and bent the jumper and it still didn't come off the shaft.
The shops in my area won't even seriously try to remove the jumper; if it doesn't pop off the shaft in 10-minutes, they just cut it off.
Plan on cutting it off. Doing so will likely destroy the gearbox seal(s). Make certain you can obtain a replacement before cutting it off.
Heating the jumper trying to get it off the shaft will destroy the seals every time.
I've got a Howse unit. Needed to change worn-out blades. First time I'd noticed, there is no porthole on the deck to access the blade bolts. Called up Howse TechRep and asked, "What th'...". Their official response was to remove the stumpjumper. Asked just how they thought that might work out. Second official response was, "Yeah, we've heard there might be a problem doing that." So I cut a hole in the deck right behind the gearbox mount that would fit a 1-5/8-in socket.
Torch makes cutting a hole easy; can use a hole saw if go slow and use oil to cool the saw. Double-check the measurements of hole diameter and location on deck.
A neighbor flipped his shredder upside down and filled it with water while heating the stumpjumper and claims to have gotten it off without killing the gearbox seal(s) but he also now uses a grease gun on the zerk he installed in the gear-oil fill port and the dang thing drips when hot.
Back to your gearbox bolts: try bending a cheap wrench to hold between the stumpjumper and deck while a willing helper tightens from the gearbox side. You might weld a socket onto a bent paddle somehow to get a fit. I think the stumpjumper will wind up coming off before its over.
I'm real curious how you proceed and your resulting experiences; please post back so we may all learn.
