225 slant 6

Pre 1975 is forged, post 1975 is cast. If you are worried about breaking stuff, go pre 1975.

Remember the \6 was developed when Chrysler built "bullet proof" engines.

Building a v8 is a simple as following a recipe. You can buy a 50 year book from SA Design that gives you that recipe and be as relevant today as back then. Building up a \6 actually requires you to think. The basics are the same, but they respond differently.