None
Yes, by everyone that offers aluminum heads.
This a variable but largely 2.02/1.60
It is a worthy move to double check. My last Edelbrock heads were excellent and ran them without issue after a check out.
Yes and no. It’s a catch 22. While you will gain performance, for less money, you can have the OWM ahead bowl ported with some throat work. This is assuming the rest of the head is in good shape.