Well crankshafts were longer back in the good ol days..
then some stupid chinese company cut it short (by about an inch) on behalf of horror fraud
to prevent it from being conveniently used on karts and bikes and such.
(also cheaper

)
And even Honda followed that example..
and nowadays 3/4" shafts are more or less all to 58mm in length (2.3")
(were 72mm or 80mm before IIRC)
So you can make a spacer from a 3/4" core drilled and keyed shaft
have the key spanning the original PTO and the extension
(and that short enough for the clutch/TC not to have lateral movement)
and you should be okay.
Many just run a long enough bolt to fix the TC driver and call it good.. so far I haven't heard of any such "bolt only" failing.
So either way it should work
'sid