Just got truck back from dealer after they installed a long block (engine). Drove home 20 miles. Drove about 20 miles total saturday. Last night went about 14 miles. Had almost gotten home and noticed it was pretty cool in the truck. I had the temp set about half way but had AC on. Turned AC off and rolled the temp to hot. Noticed no hot air. Looked and the gauge was hovering past 210. I pulled over. Tried to fill with water after it cooled down and it just poured on the ground. Drug the truck home. This morning tried to find leak. It was at rear of engine somewhere. I looked for the common causes posted on here. The tow truck came and I turned truck around to put on rollback. It was dry where I parked. So I crawled underneath while the slowly filling water in the radiater. I found the leak. It was the freezeplug between the head and the top of transmission adapter. I felt around and could feel the back of #6 cylinder. So the dealer has it once again. Some quality a brand new cummins engine and the freeze plug fall out.

 

I had to replace an expansion plug on the block below th exhaust manifold. It was bad enough I don't even want to think about the one you had problems with. Be glad the dealer has to replace it.
I made a expansion plug installer that really makes installing the plugs easier. I know that cummins has a updated part number for their expansion plugs. I belive the updated version is larger. Maybe you block had one of the older plugs installed.

 

I beleive if I had to do the job. I would drop trans x-member and lower tranny engine rear. Then I would use a freeze plug install kit. It is basically a rod with a ball on the end with different size inserts for freeze plugs. I would take some sand paper and clean the hole. Dope up a freeze plug with shelac and drive her in. Fill up with antifreeze. Jack the tranny back up and install x-member. Call customer to pick up. They had this truck before lunch and did not call me yet.

I know an engine swap witch was just done is a big job but..... You would not beleive what a not they left the engine wiring harness in. Not to mention tore the firewall insulation, scuffed up the plastic valvecover cover and lost the bolts to the cover. Oh and the air conditioning condesor looks like it has been walked on. Would not want to know how bad it would be if a general mechanic did the job. The folks are real nice so I have not said a word.