I grew up around 120th and Colorado... you're in my old stomping grounds. Of course back then all that was at 104th was a 7-11 and a fishing hole. Things have changed a lot the last 20 years... lived around there from 81~93 lived around 104th & Huron for a few years before that.

I'm with techinspector.... especially at our altitude we can get by with higher compression. I was racing 10.2:1 iron head BBC on 91 premium with 42* timing lead... so I probably could have run on 87 at more reasonable timing. If you shoot for 10-10.5:1 you'll have no problem with 91 octane. Aluminum heads you can run almost a point higher. On the other hand if you're not looking for tons of power and want to run on regular cheap gas you can go lower.... I'd probably even go at least 9:1 at that.

-Chris