only 6 comes with h-pipe/balance tube assembly for racing purposes only 8 ... and 16 formed adjustable header slip tubes plus 18 slip-on collector extensions ... transmissions except 1970 hornet 18 one tube each side over frame 19 hooker mufflers ... we recommend #2214 or 2243 24 one tube over frame left side 25 this is a tuned ... equipped with the 440 engine 27 two tubes over frame on each side 28 hooker ... sidetubes 29 fits 4v heads only 30 one tube over frame right side 31 without oil ... part number consists of headers with welded air injection fittings a hot air kit an ... with an optional racing h-pipe/balance tube assembly for use on racing vehicles ... fuel this optional h-pipe/balance tube assembly is illegal except for racing ... fit 1969-86 model years only 54 two tubes over frame right side 55 manifold dual ...