Warren, I think that is a direct thread G3, so I'm afraid I'll have to pass also. I have several G3s, but I only buy the insert style that you can screw either a 1x8 or a 1-1/4x8 into.
I believe the only way to use that one on my big lathe would be to use a 1 to 1-1/4 adapter. I tried that once with one of my old 1x8 Barracuda chucks & it just wasn't stable enough for my liking.
That's a really good chick & a fair price. I'm sure you'll be able to sell it soon.
Thanks
Edgar