The factory used shellac as a sealer, still available, pretty cheap, buy flakes, dissolve in methylated spirits ( meths in UK).
The alloy bodies are easy to distort, also the joint face on the cases tends to pull up around the mounting studs, the factory manual
warns about checking this. Remove mounting studs, clean face spotless, apply a light blue, offer up pump and squirm it, read the blue, odds are there will be two islands around the stud threads, scrape, re blue, test , repeat till happy. Set aside a quiet cuppla hours to do this, soothing music will help.
I have played around with both types of pump alloy and iron, my experience is that the timing of the gears relative to each other is a very sensitive part of the rebuild, if you can possibly mark them in such away they go back exactly as they came out your life will be a lot easier. However, this is easier said than done, I always end up marching one tooth at a time till I get the freest option, V time consuming.
If an alloy body is distorted, I dunno, I have heard of folk bullying them straight between two very thick flat things, lapping down a distorted body will not go well, you may end up with flat ends and squinty chambers.
Otherwise a flat diamond lap 400 grit will do well for lapping bodies true and end plates clean.
Last pump I did I took over a thou of each side of the body to lose end float in the gears, tediously checking end float evry so often till drag was just perceptible.. Start to finish probably took 2 days.
New pumps made to far tighter tolerances are out there if your time is precious.
When dismantled and cleaned you will see wear every where , end plates will be scored in wee circles, the gear chambers will show tracks and the teeth will be polished, the gears tend to wear more on the OD so that flat ends are no longer flat.
Theres not much to be done about chamber wear, but , gear ends can be lapped flat.
if you are careful and like a challenge good results will follow.
When the refurb work/time is considered a new spiffy SRM pump seems like a very good thing.