Update:
Okay bought chain and clutch #35 chain, 12 T clutch, and 60 T rear sprocket, so 5:1, a bit steep off the line, butgets going to speed easily.
I have had her up to about 30 mph, and with the turf tires I chose, it's a bit wobbly and scary, on my gravel road that is freshly graded.
So...