Actually, if it's the 706, you DON'T want the same heads. The 706 heads have a casting defect found in a large number that allows leaking of coolant slowly into one cylinder - I believe it's #5.
Here's how you can tell -
View attachment 362578
Actually, from my research, both the 706 heads AND the 862 heads were prone to this problem. Once you get the head open, you can see the casting mark inside, if it looks like a battery, like this:
View attachment 362579
then you know you are hosed - those are 706 heads made by Castech. If they look like the square swirl in the first picture or something else, then they weren't made by Castec. Of note, those Castech 243 heads in this pic would not be affected by the problem - it is supposedly only the Castech 706 or 862, NOT the 706 or 862 made by other manufacturers. Go figure.
The problem I ran into trying to find another set of 706/862 heads was that I could not get anyone selling any (online) to tell me if they had the Castech battery casting mark inside. Of course, I was not willing to spend money on a set of used heads and have them shipped in, just to learn they were the same thing I was replacing. It was a major PITA.
I believe a set of 243 heads like those above would work, but you'd need to do some research yourself on which heads will work as a swap-in with your motor, intake, all those things. I won't pretend I'm well versed in those things, and eventually I gave up and just ordered a rebuilt LQ9 6.0L to replace my L59 5.3L. It is a direct swap with almost everything bolting on directly - even my FlexFuel intake, fuel rails, everything. I did upgrade to the same water pump used in the 2500 Surburban, I'm not sure if it's the same as my 5.3L had.
I wish you luck, but if I were you I would NOT get a set of 706/862 heads without verifying
first that they are
not Castech-made.
