You’d be fine just boosting the n/a pistons with the original oil pump. I’ve done 30,000 extremely abusive miles at 9psi on my moms 78 300d. I do have an egt gauge, but I haven’t done any fuel mods other than backed out the Ada. It’s hard to hit 600C, takes quite a long hill. I’ve been meaning to increase the rack travel, but I also need to do the same to my 350sdl. In reality, there is time for neither and I enjoy just driving them as is.
The w123 with turbo did pick up quite a bit of seat of the pants power, it would spin 205/75/14 tires and accelerated quite well compared to before, so I put a 3.07 gear in place of the 3.42 and now it has roughly the same pickup as before.
I have an om602 in case the motor gives and a 4speed swap lined up for when/if the 722.1 lets go. In all likelihood, both will outlive me