Yes the heads are from a HD type motor was in a 1 ton commercial van, I had them cleaned up using stock valves, and pocket ported, they seem ok, I don't run up over 5K anyway, but I'm curious as to what my compression would be if I changed to new style vortec heads with the 64cc chamber. The compression on my 355 was supposed to be 9:1 with the stock heads and block which were not milled, I don't think it will run on 89 gas with anything more than that unless the timing or gap is lower.