I don't think you're going to get a pre-2k down to 250 psi without some more modification. Since you're going to go aka parts I'd get a 2 liter or Sidewinder. I expect you can get it into the 300-400 range with a stiff main spring and a heavy hammer.
Note: While I would love to take credit for his work, I am not associated with Mad Customs!
Originally Posted by senghing27
You can contact BigMatt-MadCustoms in his MCB forum