You do NOT need to swap lifters to delete the MDS, you can simply leave the MDS solenoids in and unpluggegd, or you can buy plugs from me specially made for doing exactly this that look much better than leaving the solenoids in that are unlike others sold anywhere else or you could just run the MDS with the 6.1 cam. Adding the 6.1 cam and removing the MDS are both going to adversely affect your MPG as will swapping gears, )I have 4.10s in my truck and hate em). 6.1s are usually $3500 and ocasionally a tic under $3000 all accross the US.
A low mile 6.1 will make 400+ HP plus significantly more TQ and it will run fine with the 5.7 tuning if you want to defer some of the cost of tuning up front you can do it later. A 6.1 cam and shorty headers on a 5.7 is a nice little upgrade but it will not get you 50+ HP and 40 pounds of TQ. I have done this stuff, it works. It will still use a little more fuel but the higher compression will offset some of the loss.
My son had a bad experience with leaving the MDS lifters in his 6.1 that we swapped in to his 08 2500, after 7500 miles exhaust lifters on #2 and #5 (if I remember correctly) collapsed . which lead us to swap in a 6.4 BGE. the 6.1 had 13k on it when he bought it.
On the tune....when we did the 6.1 swap it ran good, definitely could feel the difference. after he got it tuned it was much better, tore up the 545RFE in about a month, then we swapped over to a 46RH tossed f--k ton of codes, had to buy a Manual 2500 Truck ECU/PCM then sent that to out to B&G for VIN flash.
Search around for a 6.1 some people want gold for theirs , we just pick up a pair off of CL out of Central NJ for $2200, 06 Long block 110k miles, and a 2010 short block with 65k
