I too have found the FBO plates to be inaccurate on both slant sixes and V8s and I've made mention of it here before, but was run over like a freight train with disagreement when I said something about it, so I just kept quiet after that. My experience on the slant 6 was the same as what's presented here. It was getting way too much advance for the given slot length. If you think about it, from the slant 6 to the V8s, those slot lengths should be the same for a given advance amount, since the distributors are the same in that regard. .....and now people with no experience there will come out to argue with me again. But I've done actual measurements and comparisons. Even done some parts swapping between slant 6 and V8 distributors and there was no difference.