Cracked and worn out exhaust manifold?

I have a 1953 CJ3A that has a 153 cid chevy engine installed from a 1965 Chevy 2. The exhaust manifold is cracked and has been previously welded, very poorly, as well as seriously corroded, and I have not been able to locate a replacement unit. I have found a company in the US that makes a header that I am considering but have concerns regarding the intake manifold. On the 153 engine the exhaust and intake manifolds bolt together to assist with pre-heating the fuel/ air mix from the carb to help atomize prior to entering the combustion chamber. The new header does not attach to the stock intake although there is also a water heated intake manifold unit available for a considerable price. My question is will the engine still perform without this direct contact preheat or will the heat from the header, which is in close proximity, provide enough heat to operate. I use the jeep for recreation only as I hunt and fish but don't really want to spend a small fortune to make what should be a simple repair, if I could find a stock replacement exhaust manifold. I have checked with auto wreckers all over North America. It would be cheaper to possibly swap engines.