It will make installing the hydraulic pump a lot more difficult.
But not impossible.
Make sure the pump you are trying to use will be OK in the vert position. Another consideration is will it have to be shaft down or can it be shaft up. With the low clearance of the GT6K, I'd bet the thing will need to be shaft down which will possibly put the seal (and retainers) under a little harsher use.
You may be able to run a belt thru a simple mule drive of some kind and then to the pump (now horizontal)
You would be using the electric clutch, so make sure the anti spin pin is good (no sense going thru all of it just to have the clutch junk out.
Also, while a decent unit, the GT6k isn't a super heavy frame. What you build under her will need to tie into the axel mounts at the rear and the pivot up front.
I would also investigate upgrading the front axel to 1" spindles and reinforcing the steering components, if possible.