You my friend are going to have a blast in Colorado.I've already spent some time on Colorado trails in my '98 K3500 CCLB so I'm not really worried about a taking a MUCH shorter square body.
I want to swap out the engine and trans with a newer 5.7L Vortec/4L80e trans. That's what's in my '98 and I never had altitude issues since it's basically a computerized 350/th400. From 400 ft elevation in East Texas to clear over 12000 feet where I drove.
My K5 ended up being a purpose built Arizona/ Mexico beach rig
More about highway speed and sand driving with some low end crawl.
The trails in Colorado are much more about traction over rocks and the big deal is performance at altitude.
Go to the mine at Lamartine.
It is really cool.
Take the trail guide books with a bit of sketicism.They are written for Jeeps.
When you drive up the backside trails to some of those spots and you think you will get down by taking the trail that goes down the shade side of the mountain.
6 feet of hard friggen snow and water runoff under the snow pack.
The sun never hits it.
The water runs underneath the snow.
That upslope snow pack is unstable and slick like snot and washes out the trail underneath you.
And it is all fun as hell.
Pack for a disaster.
Be ready to stay wherever you are at all times.
Its a long way to any kind of help so you are very much on your own.
It will be awesome.
You will dig every minute of it.
All of that you are doing and the place you are doing it in is just more friggen fun.
I miss it and I am just amped up for you.
I think its awesome.