Planning ride along part of Lewis & Clark and Transamerica routes

Hey all,

I'm planning a long self-supported tour in the Northwest US. I had thought
about doing the Lewis & Clark Trail but the expense and logistics of getting
to the start and home from the end makes me want to do a loop, where I can
park and then return to my car.

I live in Wichita KS so it would be a good days drive for me to get to
Pierre, SD. Park the car and start riding. I'd pick up the L&C trail
(missing quite a bit of the plains riding, been there done that) and ride to
the Oregon coast. From there, I'd ride along the Transamerica Trail, going a
bit south of the L&C trail. It looks good until central WY, where the
Transamerica Trail heads south. I'd be on my own in terms of route planning
to get back to my start, and trusty 93 Blazer, hopefully still safely parked
at the back of a bike shop parking lot.

What's a good route say between Riverton, WY and Pierre, SD? I've only done
long weekend type tours, mostly in MO, where on the fly route planning works
just fine (well, except for the way-back gravel road this last tour that put
me hours behind!). I'm not at all familiar with the side routes in this part
of the country, we've been here on family vacation but didn't focus on good
bike routes.

Any advice would be appreciated!

Jack Murphy
jmurphyjr at hotmail dot com