Curt, the heat tube setup that is commonly seen on most Fenton setups these days is on the versions that they sell now, rather than originals. Original Fentons had an oem style heat riser on the rear manifold. That meant that there had to be 2 different rear manifolds for GM, since the GMC engine is longer. The reason that the riser has been eliminated on the current versions is so that the same parts will fit both Chevrolet and GMC.

Bill Burmeister