The thing is if you get the M1D, it had no disadvantage or the M1. Without a scope it is legal for CMP Garand Matches. M1C/Ds are not match rifles, the are service Grade Garand that have been modified to take a scope.
I ran sniper schools for the NG using M1C/Ds, neither have an advantage over the other in the accuracy department. If I was to get one I would choose the D over the C simply because of the price difference.
The CMP offers different grades, and the better grade will be a better rifle. Makes since.
Original M84 scopes and mounts are going to be expensive. There are after market repos, I don't have one, but I have heard some are good, some are bad. Same with the mounts. I would recommend going to the CMP Garand Forums and ask those who've have got repo scopes/mounts for an idea what works and what doesn't.
I've shot "as issued" Garand's in High Power and 1000 yard matches. Seems the worst of them are capable of 3.5 MOA. If you could shoot 3.5 MOA you'll be winning most of the CMP matches you can shoot, including the Vintage Sniper Matches.
As said, the M-84s are going to be pricy, repos iffy.
CMP is starting to sell M82 reproductions, M82G2" "Hi-Lux optics", The first M82s repos were iffy, the new, current product are suppose to be better. They come with mounts for the 'A4s but can also be used with the M1C/Ds in the CMP Matches.
The minute I received the Sales Notice saying they would start shipping in Jan, I ordered on. I'm planning on replacing the Weaver K 2.5 on my M1903A4 with the M82. My Weave is old and not the clearest scope I've used.
If the quality of the M82G2 is as good as the reports I've seen then I'm going to buy a second one and a M1D to go with it.
Again, I'd recommend going to the CMP Garand Forum and asking those guys about the bet options for mounts. The stories I've heard is the repo D mounting screw works loose after you start taking it off and on the rifle. That wouldn't bother me, I'll glue the sucker on, I have another Garand I use in Garand matches.
One thing you can take to the bank, if you have problems with CMP products let them know, they will make it right, you want find any better Customer Service anywhere.
I just don't see how you can go wrong putting together a sniper from the CMP M1Ds.