If you want a 455 crank for a 389, just buy a aftermarket crank, don't bother grinding one down. Once you grind past .030" you start to loose the hardness of the surface. I will forward this post over to my dad and uncle, they both raced '58 and '59 Pontiac's.
I also don't believe you can swap '65 or later heads to the early blocks. You will run into pushrod length problems and cooling issues.
Joe Hand
