Used Great Plains 2180 value?

Greetings,

I recently purchased a Sonerai project that came with a Great Plains 2180
engine. As the story goes, the engine was built by a guy who was trying to
make it work on a RANS float equipped plane, and just couldn't get enough
thrust for climb. The last owner of the Sonerai project bought the engine.

I know exactly nothing about VW engines, but I spent some time looking
through the boxes, and the Great Plains site. What I realize is that this
engine has every option they sell, plus some other valuable parts. The only
thing it's lacking is part of an intake (unless it's in another box). When
I add up the engine kit, accessory package 1, and the fixed secondary
ignition package, the cost is around $5,500, without counting the extra
Diehl case, and who knows what else in the box. The downside of course is
not knowing the history. The previous owner of the project said he saw it
run before buying it, but I didn't ask how long ago that was.

What I'm trying to do is decide if I want to sell the engine, and commit to
the single rotor Mazda plan (which I haven't proven to work yet), or
preserve it in case I decide to use it later. It would help to know what
something like this would sell for. Can anyone give me a ballpark guess of
what this is realistically worth?

Thanks,
Rusty