On any rocker arm setup that is not contacting and traveling in the center of the valve stem, the rocker is sliding across the tip rather than a true up and down motion, Thus you are loosing valve lift with these rockers. Your "kit" is the same one that trashed my valve stems in my original motor in less than 5K miles, as the geometry is so far off it's insane, there must have been very little R&D on that kit, or they had no clue as to what they were doing. You should not see wear at all on valve train components, if so something is wrong.
Roller rockers can be done on the 3.0 or any motor but you have to take several items into consideration. I have 1.7's on my truck now, it has custom length pushrods, studs and a rocker arm that has relatively the same length from the roller tip to the fulcrum point as the stock 1.61 ratio rockers. The new rocker rests in the center of the valve tip and the travel is equal across the centerline of tip.
The problem with your setup is what you gained in less friction in the valve train, you lost more by not getting maximum lift due to the rocker being out of position and sliding across tip rather than going straight up and down. From my measurements on my damaged motor I lost almost .035 of lift with these rockers installed over the stock setup. The seller of these kits was notified of what problems I found, nothing else was ever brought up on the boards.
If I were you I would be pulling some rockers real soon to look for wear, if you have already seen wear its only going to get worse, and you will see flat spots on the roller tips and damage to the valve tip, and soon it will beat the tip to death and the roller will break off the rocker tip. There is no way that a properly setup valve train will see this wear.
That is why roller rockers are not a slap on item for the 3.0, I have heard the pedestal mount style rockers can be made to work, I only have experience with the stud mount 302 style. The roller rocker kit that I put together for my new motor are not for a Ford at all, They are for an Olds motor, but in order to use them you need to drill the heads and install the studs, then be able to correctly measure the pushrod length required to get everything in the valve train right. They don't make a checking pushrod the correct length that will work in the 3.0, that is another piece of the puzzle that you have to make yourself.
It never fails there is someone on here every week that wants to add roller rockers to a 3.0 and most of the info given out on the topic is plain BS. The plain simple truth is you need to choose a rocker arm and then be able to adjust either the length of the pushrod or height of the valve tip to get the geometry and contact patch right. You need a degree wheel, dial indicator & your cam specs and know how to use the tools to get it right. You should see an increase in lift after installing a larger ratio rocker, which can also lead to a coil bind condition in the valve spring that you have to deal with. Most people are slapping these "Kits" on and not checking anything, or have the knowledge to check it correctly.
I learned the hard way, this "Kit" cost me a set of valves & guides, but on the good side it made me develop a true roller rocker kit that will work flawlessly on the 3.0.
Hopefully this will keep some others from following the wrong path, or cause them to investigate it further to be informed of how the valvetrain components should work.
JP02XLT