[Jonboy]

If you have the HD cooling, you will not need to mess with the radiator, shroud, or any of that. My 73 pickup was originally a 454 truck, that had a 350 put in, and replaced with another 454. They used the same frame mounts for all three engines. We swapped a 454 engine in my 74 Blazer, and used the original frame stands there, too. The 454 should bolt in, but make sure you upgrade the cooling accordingly. The TH350 will stand up to a stock 454, and the 203 case will be fine. Try to get all of the brackets with the 454, and you should be good to go.