341 hemi in 1970 dart

I have no clue where the soft crank thing came from, but that's totally inaccurate. In fact, Don Garlits himself has said and proven many times that the cranks in stone stock form will withstand in excess of 1200 HP. The cranks are the strongest part of the early Hemi.

Read this. Scroll down to the crank section. http://www.hotrod.com/techarticles/hrdp_1206_the_early_hemi_guide_of_death/viewall.html

I don't know where you came up with that info, but it's wrong.