Esch Fenton exh manifold has a tapped hole to accept a fittinf and copper tubing to route to an after market heat plate that bolts to the bottom of the intake.
Langdons sell's a hot water heat kit that can be converted to use hot exh gas.by changing out the fittings. There are other vendors that offer the kit with the threaded fittings, copper tube and fittings for the manifolds. Search CLassic Trucks, Carters and ebay.
Make sure to use dual fittings and not the single fitting plate..
