I have the older model that relies on the single screw mount, but it seems very unstable. Now I'm ready to get a real
                       mount that includes the clip guide mount. I was at Fulton Armory http://www.fulton-armory.com/ and they have the
                       two:
                       1) A.R.M.S. M14 Scope Mount, with optional Throw Lever Base (add on rail)
                       2) McCann Scope Mount quoted as a "Third Generation" Scope Mount for the M14/M1A.

                       Which one is best or is there another?

Check the Fuller Armory site again, they should have the Brookfield Precision Mount, which is supposed to be the best mount available for the M1A rifle. The M1A needs the best mount in order for it to stay zeroed. They had the mount the last time I visited their site. Good luck.  Sniper for Justice

I have the S.A. 3rd generation mount and it is very tight.  No need for locktight which some claim helps fix mounts on large caliber weapons, which IMO indicates poor design if you need glue to stabilize your mount.  I tightened it down hard and once I zeroed that baby it has not moved since.  

I failed to mention that I have one of the SA 3rd generation scopes which are very good but kinda heavy.  The whole package is 12+ pounds but deadly accurate.

I had first a 1st generation. and then a SA 3rd Generation, and never could get the zero right. The 3rd generation one I had my gunsmith lock tite and boresight. It would still stay in the black at 100yards, but the pattern wasn't there.
[sniper]
It was one of the few rifles I shot better with iron sights than scoped.
My solution was to get a M1A Scout.

Armscorp also has a mount that also sounds like a good 3rd gen, maybe 4th.  Then they have a $158 special instead of $195. I'm wondering if it also "cams into the alignment groove on the receiver", and will send an email to them.   Here's a partial writeup:
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The Brookfield and McCann mounts allow for this "misalignment" by providing lateral adjustment of the clip guide block during installation. Properly installed, the
screws are in shear only, with no bending moment on the mount, as good practice demands if the screws are to remain tight. The Brookfield goes two steps further. It
cams into the alignment groove on the receiver, ensuring 100% lockup in the groove. Then it adds a stablizing screw as the Armscorp mount does.
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ARMSCORP M14 Solid Steel Scope Mount. Our M14/M1A Scope Mount is the best on the market at a price you can afford. Machined from solid steel, this
mount has the strength you'll appreciate and with our system, unlike others, you can use iron sights without removing your scope. Our mount installs very easily, has
positively alignment, and a very easy process for even the most inexperienced shooter. With Armscorp's NEW positive Locking System (Patent Pending) and re-zero
feature you'll be a sure winner.
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That "sure winner" bit really excites me[:\] (whoops 3rd party writeup)[:\](no, copied from Armscorp site [:\] [/url]http://armscorpusa.com/Products/m14scope.htm[url]