What the heck is up with my timing????

[Bandit]

I put my engine all back together yesterday and i went to time the engine. I got #1 to TDC and installed the distributor so the rotor would be near dead on #1 on the distributor cap. Sure enough, it fired up and ran fine. Then I got out the timing light to get it to 6 degrees BTDC, but the timing mark is out by about 180 degrees. What could be wrong, I had the vaccuum advance plugged off, I don't know what could be wrong. The truck runs just as good as it did before, so do I leave it? Is the distributor out by a tooth? Also, the distributor cap itself is sitting roughly in the same position as it was before. Is it possible the timing marks are on the wrong side of the block?

Thanks

Bandit