I have read often,but never posted,hope this is correct...Have a 71 or 72 340,built 40 years ago, very lumpy purple cam, just know you're rolling on floor now,anti pump up lifters,stock rockers,dual plane Holly 650 double pumper,Accel dual point,no vacuum advance,Echlin Super coil,stock 340 manifolds,2" exh,with 2" custom side pipes,ok stop laughing now,engine bought out of reputable salvage yard has "Z" letter cast on heads,has surprised myself and others on road track and street as well.With the deep wealth of knowledge you all possess,can anyone explain the "Z" significance ? I built the car myself 40 years ago,really! I am now 76 and I am determined to have a go with it again,while still able.Oh,and the engine currently has less than 10,000 original miles,I bought it with 7000.yeah N.S.