You guys are right, I was scratching my head wondering how we got away with it on that one, that truck was an 04 with no MDS.

We did one (non MDS 5.7 into a MDS 1/2 ton) on a 2011 and it would not set the CEL or trigger an MDS code if we always ran it in manual 5th gear, if we left it in "drive" it would set the code and turn on the light as soon as it tried to use the MDS.

You could still put in a 6.1 long block and use your MDS cam, lifters and solenoids, you would still have more compression, displacement, cylinder head flow... I did a similar thing on my current ram 2500, I put in a 6.4 BGE short block with 5.7 cam, heads, intake, exhaust... makes awesome TQ and the stock computer is running it all just fine.