Helped my friend replace those cooler lines at his shop a week ago--had to take out the drivers side motor mount bolt and raise the engine up before they could be snaked out from between the engine and crossmember!...after we got it all back together with 2 new lines and the block O-rings,it still weeped oil out of where the O-rings go to the block...

...so the customer has to come back soon to try again...
I suggested doing what I did to my 6.2,just make a loop out of 3/8" copper tubing and bridge the two cooler ports together...he didn't like that idea though...funny thing is,on my truck,neither of the cooler lines had any oil come out of them after I cut them off,even if I blew air thru them...I bet nothing ever made it into the cooler!...so "deleting" them didn't harm anything,and I dont think the cooler in the radiator does all that much anyway..
I know of many one ton dump trucks at cranberry bogs that no longer have the oil cooler hooked up,if anything was to blow up it'd be those trucks,they get abused badly!...guy who does the fleet maintenence showed me a cooler he cut out from a 6.2 radiator he replaced,it looked like someone stuffed gunpowder inside it and lit it up,it was all puffed up!..
I bet those cheesy OEM oil cooler lines made GM a lot of sales of new trucks and engines...mine had the crimped areas rot completely off on the side facing the ground you cant see,the top side looked perfect too..surprised the rubber didn't blow off the fittings...