Now, on from the ideas to the what to buy and how to do it stuff.
To replace your progressive rate springs with single rate, you'll need 14" springs (P1000 5-seater.) On the front, those springs will be 2.5" inside diameter. On the rear, you'll need to go with 3" ID springs, unless you want to get rid of the plastic mud guard in there - then you can use 2.5" ID back there as well.
The spring weight will be your choice. What I'm seeing here is that most of the guys like to run 250 lb springs on the front, and 275-350 lb springs on the back, depending on how much they haul around and how they like their ride.
I chose to go with 250 lb 2.5" diameter on the front and 300 lb 3" diameter in the rear.
In spring lingo, these are referred to as:
2.5 x 14 x 250
3.0 x 14 x 300
I have found a surprisingly low number of suppliers out there for springs.
Summit Racing has a great selection and low prices on the 2.5" ID springs (and free shipping over some amount) but they're price nearly doubles on the 3" ID springs, leading many to consider ditching the mud guard.
Daves Offroad Supply is a little more expensive on the 2.5's, but not nearly as bad on the 3's. I had grown fond of the red springs with my white machine with white a-arms, and Summit springs only come in silver or blue, if I recall correctly. Dave's had red ones, I could get 3" for the rear, and overall paid about $20 more with shipping and everything than I would have paid from Summit.
Anyone finding more sources, add them here for other shoppers!