As someone who has spent at least an hour unsuccessfully trying to install a set of clutch shoes without the clutch spring tool, it's a godsend.
"thought the k4.6 would be identical to the 5.9 with same flyweel"
The flywheel in your pic looked like it came off a buggy.
That's not to say that it's impossible for you to adapt it to work with the Savage (a shorter collet perhaps), but even then, ya gotta yank and reinstall the shoes.
The only out that I can think of for you to keep the current flywheel in place and not have to remove/reinstall shoes would be if you (let's say) have multiple shims under the clutch-bell and can pull a shim or shims from under the clutch-bell and place it/them on top and closer to the spur gear.
That would effectively move the clutch-bell (and its gear) back and closer to the engine.
It's the flywheels, not the engines.
For all practical purposes, the two engines are more or less identical in how each would fit into your Savage.
I'm willing to bet that you would have the same situation as you do now (with the engine with the buggy flywheel) if you swapped the flywheel arrangements between them.
I have turned the carb around, swapped engine mounts over too 😅
Making progress!