Everyone I talked too ref: the repo M84s were not happy with them. The same for the early M82s.
But the latest M82s are of excellent quality. To the point the CMP started selling them. The CMP M82s are later model HiLux and come with mounts for the 'A4.
The M-82s were used on M1C/Ds, therefore are legal in CMP Vintage Sniper Matches. Rule 4.2.3, Table 2, "Legal Vintage Sniper Rifles and Scopes"
I don't have a M1C/D, but I've used several in running National Guard Sniper Schools using the C/D's. The M84 (originals) work but they have a rather thick post sight (as does my Weaver K 2.5). The M82s also have a post sight with horizontal wire, the difference is the post is much thinner on the M82.
With the M84 and the K 2.5 I had to use a 6 o'clock hold where as with the thinner post on the M82, I can use it as one would use a cross hair. Just the top of the cross hair (post) doesn't go all the way to the top but you have enough you can center it like a cross hair.
As I said, I have the Weaver K 2.5, but I got a CMP repo M82 and put it on my 'A4. I haven't shot a match with it, but from what I've seen shooting it so far, I can do much better with the M82.
PLUS and this is a big plus, the Repo M82 is sealed, the original's weren't.
Both the M82 & 84 have half min clicks, so there is no difference there.
Anyway, I'm registered to shoot the Vintage Rifle Match in the CMP OK City games in Aprils, I'll use the M82 and compare the scores with the matches where I used my K 2.5 and see which one stays on the rifle.
Back to the M1D: Everyone has his/her opinions, based on experience and how they use the rifle so take my opinion for what it is, "my opinion"
If I was to build a M1D, (which I will this year) I'll go with a CMP service grade D, and use the CMPs repo M82. I would go with the original mount, though more expensive. I've heard too many bad stories about the repo mounts.
Since I'm into shooting as opposed to collecting, I do with an after market check peace. I wouldn't put on a muzzle brake/flash hider. In my sniper schools we found out the detracted from accuracy. I'm not trying to hide from anyone and matches are in the daylight so I see no need.
The main thing, after glass, is to get the cheek piece property set up. It isn't designed to get your head higher on the stock, its designed to push your head away from (to the left) of the stock so your eye lines up with the offset scope, allowing you to keep your head straight.
Good luck on you M1D, and take it to a CMP VSR match, let her show you what she is capable of.