Years ago I installed the Fenton exhausts with an Offy 2-carb manifold. This is not the ideal configuration because one has to grind away some of the intake manifold to get the hold-down bolts to work.
Aside from that, I made a heat plate for the bottom of the manifold out of 1/4 inch stock with two holes drilled and tapped for 3/8 pipe fittings. With some more fittings and bits of copper tube I have a manifold heater. It has worked fine for twenty years except that I did have to tighten the fittings in the Fenton bosses and the plate twice. Assembly of the manifolds, gaskets and bolts takes at least three hands.
