Hi Timothy!
Like Gary said, I'm right in your neck of the woods. I work just down the hill from KBJC and live at Parkland (7CO0) just a little North and East of KEIK.
I bought a stock 1966 150F back in 1996 and flew it that way for 9 years before converting it to 150HP.
There is a huge difference in performance up here between a 150HP 150 and a stock 150. Climb rate in a stock 150 is around 200-300fpm on a good day. A 100HP 150 will take off and fly just fine but it requires more precision and patience in order to get the most out of it.
When I had my 150 with the O-200 in it, I had it over 12,500 several times and flew into Laramie, WY several times. Joel Kiester lives in Boulder and has a 1959 150 based there. He's flown his around here for years and even routinely visits Westcliffe in it. The West coast contingent flies to Clinton, IA every year, usually crossing the Rockies along I-80 with stops in Evanston and Rawlins. It can be done.
However, stepping back to 100HP after being used to 150HP would be quite a shock. You would probably be happier sticking with a 150HP plane if you can find one you can afford.
Welcome to the club! Good luck and have fun in your search. I'll send you a private message with my contact info. Look for a flashing envelope next to the "My Stuff" link near the top of the page.