The exhaust manifold is the Achilles heel of the CCKW and DUKW, in the 1950's stronger reinforced ones were made for the British Army, one of these was fitted to the CCKW I used to own and it completely overcame all the problems of distortion and cracking. Rex Ward has been trying for several years to get suitable heavy duty manifolds manufactured, latest news is that they will be available soon, see
www.dukw.freeserve.co.uk
I have no connection with Rex other than as a satisfied customer. Hope this is of some help to you.
