Probe starts
175W = ANSI M57
250W = ANSI M58
400W = ANSI M59
Pulse starts
175W = ANSI M137
250W = ANSI M138
400W = ANSI M135
150W HQI = ANSI M81
250W HQI = ANSI M80
As far as matching ballasts (probe vs. pulse) to lamps, best thing to do is try to decide on a lamp you want to use, then look up what ballast is best for it. This information may be harder to find but usually manufacturers and vendors post some data.
And while it's best to match a ballast to a lamp, it may not be a hard and fast rule. I use Ushio's over one tank, 175W, according to Ushio I should be using M137. But I use M57 because that's what I have. The lamps work. They may not start as nice as they could and they may not be as bright as they could be, but they're nice and they work and things look good under them. So if you can get these ballasts for cheap or for free, it's probably worth it, as long as you're OK doing your own wiring for them (it's not that hard).
Advance, one of the larger maker of ballasts, has a lot of info on their website. You can go to the HID ballast lookup section directly with this link:
http://www.advancetransformer.com/ec...hid_lookup.asp
... Or by going to the front page (
www.advancetransformer.com ), then selecting "Catalog -> HID Lookup".
Hope this helps..