I'm looking for the final word on which '68 tic toc tach redlines go with which motors. Searching this site says (and what I thought) - any sm block = 5K tach (except Z-28). Low & mid horse BB = 5.5K, and the 375hp BB & Z-28 = 6K tach. Now the repops have shown up, vendors are all over the board with what goes with what - which prompted an argument last week with one of them -*that should know*- on mismatches. What is the final answer? Thanks to all!