RE the distributor, an MSD will be 100% brand new, not worn out. Original, even in the best case is going to have wear because parts are not available to truly return them to like new condition. Pertronix now produce a Y-Block distributor, which gives another option.
You won't need posted G heads for a street build. If you already have them, they are better but if you do not, don't get hung up on that. It will make it a much easier task to find the heads, giving you more options.
What kind of power are you shooting for?
Lawrenceville, GA