Robb is basically correct. On a carry/self-defense weapon, this additional safety makes perfect sense. If you want a competiton/race gun, then you may shave a few ounces off the pull. Hardly worth the savings on a carry gun.
Keep these extra internal parts clean and lubed (like you should be doing anyway) and the extra "series 80" parts will not be a hinderance.
If you want to try your 1911 without the series 80 parts you will have to get a filler piece,called a shim,from Brownells..
It is rather expensive,about $3.00 if I remember correctly..The postage will kill you,thing to do is order when you need other things..Not too hard to get a order together,just spend a bit of time with their catalog..