with our sixs having poor combustion chambers, they like timing. i'd bet n/a timing could go as high as 36-38 or higher. old BB chevies like timing too. once the boost comes into play start taking out around 2 degrees per lb of boost. i have had bad luck with pertronics kits and high performance use. one reason is timing control @ higher rpm. the old mechanical distrib with worn out centrifical mechanisms would tend to scatter the timing at higher rpm.
revod, are you also using a performance coil?
with the old motor , what were your shift points? i bet the v8 liked them higher than 5k rpm, the governor may need to be adjusted to bring them down. tom
