subgy

Detonation can occur if too low octane fuel is used in a higher compression engine and / or ignition timing too advanced etc http://www.misterfixit.com/deton.htm

Makes sense and a lot easier to improve on what you had. The RB engines were the best thing about the VLs, a tweeked one of these would totally vapourise a V8

Sounds like you've gone through everything just re check again . I would suspect the new HT leads could be of poor quality and are breaking down when get warm. Have had this happen on an HJ Holden 173. Did you replace the HT lead between the coil and distributor as well? also check low voltage connections in distributor between points condenser earth if anythings loose - not conneced up correctly