I've used a number of different scope mounts throughout my experience with the M14 clones. I've used to ARMS 18 and all three generations of the Springfield mounts. The inability of the Springfield mounts to hold zero is due more to the "quck removeable" design than it is to the aluminum that they use to make the mount. The ARMS is nice but too short for the scope that I use. Springfield Gen. 3 scope mount I use now does hold zero, but it requires locktite on the threads of the mounting screws, and the screws have to be really tightened up. Obviously, that's a semi-permanent mount.
Sadly I haven't been able to find a reasonably-priced Brookfield in the 3 years I've been searching for one. I've only seen them for the $450 ++++ range, going as high as $675 for a new one.
The M14 is just a really shitty optics platform. Any scope mount that works will be a permanent mount, period. If you don't mind not being able to use your irons that won't really bother you, but forget the idea of a quick-detach type rig that the AR-15 loves.
Another factor that you'll quickly notice is the comb of the stock. The stock is just not "scope friendly" as one might say. The stock's comb drops way too much. I actually have to use a slim strap-on cheekpiece just to get a proper cheek weld for the iron sights. For the scope I use a big ugly mound of duct tape and styrofoam.
To be completely honest with you, I'd keep the M1A as a "pure" rifle and just use irons. Buy an AR-10 or FAL if you want a decent scoped autoloader.