These shrouds will fit engines equipped with Super Flow heads or Competition Eliminator heads. You will notice the shrouds different design to accomodate these heads. These shrouds are available in NO HEATER ONLY. And are available in 3 different widths to accommodate engines that have been built with stock length rods 5.4" or engines with 5.5"-5.6" rods and 5.7" rod lengths. If you are not sure as to what rod lengths you have in your engines, simply measure the width of the engine from the top center exhaust stud to the other side's top center exhaust stud. For a stock length rod engine it should be approximately 20". Engines with 5.5" or 5.6" rod lengths will measure out 20.5" and engines with 5.7" length rods the engine width will be 21".