the best way to slam an elcamino? is it possible with coilovers?

Sure its possible. They sell bolt in kits for the front. The rears take a bit more work, but can be done. Not cheap as you probably already know.

Sure its possible. They sell bolt in kits for the front. The rears take a bit more work, but can be done. Not cheap as you probably already know.

what would be the cheapest way?

The cheapest way is to cut the spring. I don't recommend that.
You can get 2" drop spindles for the front for around $250
Drop springs for the rear for around $150.

If you want it on the groud air bags $2000-6000

What's a website that sell a bag setup? is there a how to?

Air Ride Technologies.

Here is a link http://www.ridetech.com/