Ballast ?'s (tech help needed)

I have 3 HPS Securtiy lights (150w each) and want to run MH bulbs. Do I need a different ballast or can I use the same built in ballast and just change the bulbs? Thank you

Normally you can add a switch to turn off the ignitor with an HPS ballast to burn MH bulbs but since your lights are 150 watts, I don't really remember seeing any MH bulbsthat are 150 watts other than the HQI ones and I'm not sure what they run on.

I think the best thing is if you want to make it switchable is to start with a 250 watt ballast or larger. Then you have access to standard bulbs.

What kind of HPS ballasts are they S55, or S56? And what size capacitor is in them? (Should be printed on there and labeled with mfd, microfarad, or µF)