Closed chamber heads for 273 in S. Calif.

So a request to Rock Auto for 86-'89 D100 318 heads will include the ...302, ...646 & ...714 heads, because they are all the same, except for the casting #'s, right? Is there a left and a right?
Also, do they insert new guides? Is there a choice for new valves, e.g. stainless? Do they tell you how much they milled off the head surfaces or what the volume of the combustion chambers are?
Will I be able to use my 273 rocker arms & pushrods?
Are they helpful?