I have 2 Lee-Enfields, neither one of them are well machined. One with the not-so-good bore had its blueing/paint removed with acid by me. This is the rifle that will be converted to a .44mag later. Since it will be a custom built gun, I though I might as well smooth up the action for appearance and practice.

Once that piece of steel is in the white and one start to file/stone/sand it, all the imperfections seem amplified : very rough machining marks, tiny bubbles in the steel, and all "flat" surfaces are as flat as cakes...that had been sat on. On some surfaces, I can remove 90 percent of the marks, then there is a long, deep one that is I guess about 0.005" deep, right in the middle. Internal surfaces are fine though.

This drove me to think : There are good Mausers and bad Mausers, would there be good and bad Lee-Enfields? Hopefully there are and I can learn to spot one to reduce future workload, although after many hours spent on this action I am starting to like the way it looks.

Sounds to me like you have a typical Lee Enfield. I doubt there are any real good ones when they are compared with the fine DWM and Mauser built rifles.
The brand new 1908 DWM mausers which were commonly available in the late 70s were truly beautifully made. The 1935 Oberndorf Mausers available at the same time were likewise top quality. In general, I doubt that the military arms of any other type matched the various mausers as far as workmanship was concerned. The closest were the various Krags. The US 1898 Krag was one of the really nicely made military rifles as were the military 95 Winchesters. Earlier the trapdoor Springfields exhibited some pretty fair workmanship.
The British military arms were always ultra functional but seldom attractive at any level. I've never seen an 03 Springfield which was anywhere close to the European arms in quality of fit and finish either. Regards, Bill.

I have about 4 No 4 Enfields right now.
I interact with them by mounting scopes and shimming the bolt face for less headspace.

I always thought that the "springy action" was an urban legend, but I went through an analysis of the deflection, and it may be springy enough to affect the brass. I need to do some tests.

Clark,
There is no "may be" about it. A simple demonstration of the deflection of the bolt is possible. Chamber a #4 to a negative headspace dimension. Say -.002 It will be possible to close the bolt with some effort. Try the same thing in a p14 and you will find it impossible to close the bolt all the way.
Anyone who has done much shooting of a Lee Enfield and reloading for it (as I have for forty years) will have seen the effect on the brass of heavy loads in the #4 action. Ouch! Regards, Bill.

My very first "big" gun was an Enfield. ($16 bucks thru the mail, with 500 rounds of ammo and a cheesy side mount 4X scope) I have looked at many of them, all with a fondness one has for the "first". Every one of them lacks the finess and finish that define a "fine" rifle, however, it would be hard to pick a better example of a utility rifle for the farmer, rancher, outdoorsman. "Takes a licking and keeps on shooting". Need a saddle gun, truck gun, knockabout gun, it fills the bill. Having said all that, if fit and finish are your bag, forget this old gal, it will always want to be a utility gun. But a fun one.