4.6 Questions

The old 5.0L blocks may have gone South at 500-550hp, but the modular block with forged internals will take in the neighbourhood of 1000hp, so don't count on it cracking any time soon. The Mark VIII block isn't a bad idea either. The heads and rest of the components won’t work, since it’s a DOHC design, but the block will. Not necessarily from a strength perspective, but the aluminum block will save you some weight over the SOHC iron block. Just keep in mind, that with an aluminum block, with aluminum heads and an under hood turbo set up, you're going to see a lot of heat soak with daily driving.

As far as the transmission is concerned…..with any mega horsepower car, the need to address the rest of the drive/power-train arises. Were I you, I’d consider a built 4R70W to match the turbo 4.6. It will perform better than any stick and can be build far stronger, for less money in the process.