The factory spring is 16 # on a full sized 1911. Are you planning on shooting some target ammo ? If not, get that spring out of there as you will hammer the frame pretty good and cause a possible timing problem.
If you feel the spring needs to be replaced, Wolff has a 16 # varible power spring that will work very well.
In fact, I replaced mine with a 18lb spring. So far there has been no problems with either light loads nor heavy loads. Even on my Gold Cup, it came with , I believe a 12 lb spring for light target loads, first thing I did was put a heavier spring in.