1999 Silverado 2500 6.0 Heads

[Lostaf]

I hope this is the correct platform. Forgive me in advance if it is not (maybe redirect me?). Problem: Kid blew head gasket. Removed both heads, pressure tested, one came back bad (apparently previous owner ran exhaust bolt into water jacket). Went ahead and had parts guy order me new gasket set, new head bolts and 2 reman'd heads. Paperwork says heads from a Yukon 6.0. Having to work 60 hrs week, I hired  a mech to come install heads and get truck running. He called me saying head bolts are wrong. Threads not long enough.... I back sourced the bolts and they seem to be correct (3 different parts places). I do not know where to go from here. I wonder if wrong heads?? Incompetent mechanic? I have not been home yet to compare new bolts to used ones, trying to seek some input on what else I can look for. I am mechanically experienced but not to the point of knowing this kind of info. 

Any help in a contsructive direction would be GREATLY appreciated!

Please forgive me if I missed needed information. 

Thanks in advance!

Kevin

[txab]

Mechanic matched the old to the new? Difference in head maybe? Dunno...never had this issues myself

 

This should be the set for one head.

 

 

Fel Pro ES72173

 

 

Bolt Diameter	11mm (Bolt 1); 11mm (Bolt 2); 8mm (Bolt 3)
Bolt Critical Length	155mm (Bolt 1); 100mm (Bolt 2); 45mm (Bolt 3)
Bolt Head Size	15mm (Bolt 1); 15mm (Bolt 2); 10mm (Bolt 3)
Bolt Thread Pitch	2.00 (Bolt 1); 2.00 (Bolt 2); 1.25 (Bolt 3)
Bolt Thread Length	55mm (Bolt 1); 85mm (Bolt 2); 32mm (Bolt 3)

 

 

[CamGTP]

Factory 1999 6.0 heads are iron heads. Are the new heads aluminum?

 

That would be the only differences I know of, not sure if the head bolts are different from the aluminum heads. People always swap heads because the iron ones kind suck eggs.