400ex fronts work?

Depends on the blaster....

I have LTZ400 front shocks on my blaster (nearly the same length at the 400ex shocks) but I specially made my front suspension to accommodate them.
 
They will not work with stockers. It will chew the ball joints to pieces because the shock would no longer be the limiting factor on travel, the ball joints would be...

The best you can do with stock a-arms is banshee shocks (on the cheap) or aftermarket shocks. Used works steelers pop up every so often relatively inexpensive.