I wouldn't give up on the 327 just yet. Check out the fuel system and run it some more and see how it does. The odor could be coolant so possibly head gaskets are in order.
The 305 has a roller cam and can be a decent runner. However, some of the components are different. The flywheel or flex plate from your early engine will not fit. Also the Camaro was fuel injected, and early intake manifolds will not fit. There may be some issue with the fuel pump as well.
Fred
