The only issue with a D66 is the added mass of the larger compressor wheel results in more force required from the turbine section to spin it, and that means a higher drive pressure to drive it. The 38R is ball bearing, so it takes less energy to spool compared to the cartridge bearing you have now.
If you are going to change injectors I've recently done extensive research on this planning my own mods, I would look seriously at a 175/80, or if you want to stick with the same size go to a 160/30 or even 160/80. The ability to inject the fuel in a shorter period of time with a larger nozzle means you can run slightly less timing and finish the injection earlier, valuable for keeping EGTs and cylinder pressures in check. This will be especially helpful with a D66.
As for lifters, unless you suspect an issue, I would not change them. You have set wear patterns on the cam lobes and rollers, on the lifters and lifter bores and guides. If you suspect a sticking lifter, I'd strongly suggest Archoil AR9100, if not permanently, at least for two oil changes, it has a tremendous cleansing effect as well as it's lubrication benefits. I'm running it in my E99 right now, having seen the cleaning benefits in my 6.0L between tear downs.
The Current Truck (Oct-2013 to Present):
1999 (Early) F-350 Lariat, CCLB, SRW, Black/Tan
7.3L Powerstroke, 4R100, 4x4, 3.73, 37x13.50-18s, '05 Axle Swap, 6" Fabtech lift, GTP38 "D66" turbo upgrade, SCT 4-position chip with custom tuning by me, Straight Piped 4" down pipe through 5" dual stacks, N-Fab full length triple steps, Pro-Tech cab guard and tool box, louvered 5th wheel gate, Hella 500 Fog and Driving lamps, much more to come...
The one I'll miss, (Mar-2009 to Jan-2014):
2000 Excursion XLT 4x4
6.8L V-10, 4R100, 4.30, 285/75-18, 271whp / 388wtq
The one I won't, (Jul-2005 to Sep-2012):
2005 F-350 XLT, CCLB, SRW, 4x4 FX4
6.0L PSD, ZF-6S650, 3.73, 35x12.5-18, 4.5" Lift