Dear Buick faithful, I have a 66 Skylark GS, but the original 401 was replaced with a ‘63 401 (it has a JT stamp). I was checking the timing and it is set at 0*. The book on 66’s says 2.5* but the specs on a JT says 12*. The balancer has marks at 0, 5 and 12 only. So my question is, should I leave it or move it to 2.5 or 12??