First Timer, I'm the proud ower of a 06 Jeep Commander 4x4 Limted 5.7. I purchased Used back in 2011 with 60,000 miles. My wife drove this XK around until 3 months ago with 140,000 miles when my Hemi dropped a valve seat destroying the #5 cylinder walls and piston. We purchased her a new car. And I got me a new Toy. I decided to replace block And damaged piston. Basically just had engine rebuilt. I've placed block back into Engine bay. As I was beginning to install roller lifters I've noticed that I've had two different types of roller lifters. 8 are rounded off at the top where pushrods sit and the other 8 are squared off where pushrods sit. After looking into the Internet, I found that the rounded off lifters are Non- MDS roller lifters. Is this correct? I'm guessing someone deleted MDS, prior to me purchasing this XK. I've driven this Jeep to West Virginia from Texas several times. I do remember my mileage being no more than 16mpg. How can I tell if my MDS was actually deleted? I've posted two pictures 1- of Roller lifters and 1- of the XK. I'm looking forward on learning from Y'all. I'm eager to get my jeep back on the road.