I've got a 72 108 4.5, with a XR-700, and an MSD 6-AL. The plugs are Champions gapped at .050. I'm getting 20 lbs of vacuum at 40-50 degrees Before 0. Prior to this I was keeping it to a more conservative 5 degrees before and getting only 17 lbs of vacuum and very stodgy performance. My question is, since the vacuum advance pot will not allow any more advance since it hits on the fuel line, should I remove the distributor and back it off another tooth to get a few more degrees of movement? Also should I attribute the timing marks being so far off to my modifications or from someone botching a distributor installation?