If you are talking about a 1911A1 made in Argentina in 1927 for the Argentine military, you probably can shoot +Ps if you want to stress a 70 something year old pistol. If you are going to use this for a carry pistol or any sort of personal defense handgun I would suggest you get a recoil spring kit from Wolff Springs (probably a 20 lb set woudl work well and help save the pistol) and a new GI barrel from one of the large distributors who advertise in the shotgun News. Check first with our sponsors to see if any of them sell 45 barrels, it might save you a few bucks.
I have one of those pistols and wouldn't shoot +Ps. Although these handguns were made on Colt machinery set up in Argentina at the request of the Argentine Govn't, the steel used is old and (IMHO) not up to the same standards as US Steel. But even in a 70 year old American made 45 I wouldn't shoot +P. Isn't worth risking the pistol with high pressures and I'm not sold on +Ps in 45s. Mikey.