OK......Heads needed to be welded? Waterjackets? Some of those places you can't even get too.
How many welds? If its more than 1 (and don't take this the wrong way) I would just throw those heads away.
Aluminum is very delicate to weld on. How do you test their welds? Validation of repair work is always critical.
Its not worth the risk of putting them on only to have a nagging small coolant leak.
Will they at least warranty against leaks?
I don't even like welded blocks and iron is much easier.
All your external parts look very pretty! Awesome Job!
In answer to your very deep cam question....I have no idea. I'm not an engine builder, thats a pretty specialized skill.
I buy defined short blocks, long blocks and slam them in. I've done heads and cam but not in an empty block.
You need an engine builder mentor.....someone who can help you navigate the process.
Maybe LS1Tech......lots of 6.0L guys over there....camaros & some trucks.
Or youtube.....always good for education....some take questions
(5) How To Build An LS Engine - Assembly Part 1 - YouTube