I got these headlights off eBay and the manufacturer changed the bulb to H1's. So I ordered H1 8000k HIDs from HIDextra for my lows. The HID bulb was bigger than the hole for the stock H1, so I drilled it out to get it to fit, but the bulb is also long enough it hits and has to angle under the cut off in the projector so it pushes my bulb down. So I had to crank the angle of my headlights up so much that when I hit my highbeams the are UP in the trees and of absolutely no use except to try and find birds or flash my highbeams at the international space station.

http://www.ebay.com/itm/190886820877?redirect=mobile
If link don't work search. EURO BLACK 98-04 S10 BLAZER HALO PROJECTOR HEADLIGHTS w/SMD LED+BUMPER LIGHTS

 

Do both the hid bulbs and the halogen bulbs look like h1s? If they do, you could try using a spacer on the back of the bulbs, but it might (read: absolutely will) affect the output. If you could post a pic of both sets of bulbs we can be sure that they are matching bulbs. If they do match, the hid capsules are probably too long for the projector and you'll have to spacer them.

If you can't get it figured out, you can always do a retrofit.