69mach1377

The conversion kit option for me would only start the snowball effect because my current heads would become the limiting factor. And that could lead to more induction options, tranny and rear options, etc..$$$
Budget plays as big a role now as it did when I first built my motor.You are in the planning stages to get it right from the beginning, as your budget allows. Getting the best combo of parts should be your primary goal.

67mustang302

You're better off starting with a late model roller block, since the cam selection will be cheaper that way. Might as well just built a n/a 408 stroker and shoot for 500hp at the crank.

As far as strength, either early or late block, you don't need to worry about power levels until you're pushing 600+ at the crank. And there are guys who have run late model blocks with jacket cement and put down over 600rwhp, which translates into around 700 at the crank.

Keep this in mind....most block failures result from 1 of 2 things, too much power or a bad tune. Many blocks have failed because the tune is too aggressive and it's really hard on parts, and the stress and vibration from a lot of timing and a little fuel causes block failures.

As far as too much power, whether it's an early or a late block 351w, if you are at the point where you will have to worry about either one due to power output, you're already into the realm of building $20,000+ engines.