I just got a HEX pickup and a GR-55 interface. the only problem is that MIDI Guitar 3 won’t let me select the “Channel 1 … 8(HEX PICKUPS)” in the Audio selection menu. It just keeps changing back to “Channel 1+2”.
was really looking forward to using the HEX mode of MIDI Guitar 3…
unfortunately the gr-55 does not provide six input channels.
the gp10 or sy1000 in combination with any of the gk2/3/graphtech/rmc pickups will give you the 6 inputs.
a breakout cable with a multichannel audio interface is another option for those with pre-2025 gk hardware.
No way! I picked the wrong one!? 
, So I should have gotten a G-10?
What’s a breakout cable? Can I just do a midi cord out to my computer at least you think?
Thanks for your reply 
Unfortunately you missed the advice given by @kimyo in this answer:
A breakout cable has on one end the GK 13-pin plug and on the other end six TRS plugs that carry the signals of the single strings. For this solution you need a audio interface with at least six inputs.
i don’t see any gp-10’s on ebay or reverb, aside from the crazy expensive listings from japan.
building your own cable is an option. there is a pre-wired part which can help, but it ships from australia (gumbo’s 13 pin pre-wired jack, don’t have a link handy but i’ll look if you like).
the gk pickup requires power. the simplest solution uses two 9v batteries.