What we could use is a sub transmission like a trail 90.
Working on that. Could be awhile.
Meantime I'll have to carry some chain. I called TBI's tech folks. Good service, but they don't normally offer anything over 61T.
Sposeta call me back tomorrow and tell me whether or not they can do a 70.
We've done 500 mile slab trips on my Bighorn2 with a 55t. Figure on a 10+ mpg hit and a bit of extra time getting up to speed here and there, but nothing objectionable about it other than that.
Thanks for the tip on the sprocket. I may yet need another source if anyone knows of one.