Long story short heads on my 4.8 took a dump (leaking coolant) and I'm thinking of swapping to the 243/799 but I can't find info on PTV clearance issues, which head gaskets to use and so on. I'm not sure if this topic has covered and if so by all mean direct me to the thread.

 

PTV is the exact same, headgasket is the exact same.

799 243 will lower your compression down to ~9.2:1.

 

So basically it's just bolt and go? maybe a little milling to keep the compression?

 

^^^^^^ Boom!

 

You'll lose power going to 243s if you don't mill them to get compression back up.
The 4.8 isn't exactly choking on its stock heads, there isn't much (if any) gains to be had from the increased flow. The only way you'll see benefits are by keeping the compression up to at least stock (or higher).