I am thinking about stroking a 351w into a 393 for my '70 Mach. What are the best 351w blocks to use for a roller camshaft? I know if I use my '69 351w block that I will have to purchase the roller conversion and have to do some block work. Are newer model 351w blocks better for this 393 stroker idea? If so, which year models or casting numbers are good and which cars or trucks received these blocks? Thanks.