Why not consult "The Blue Book of Gun Values and/or contact The Winchester Collector's Club;
http://www.winchestercollector.org/
I'm no expert on the 71 although I have other pre-64's and for my money if a rifle has been altered in any way it seriously adversely affects its collector value. Further as rare as the 71 may be there'll always be another. Inform yourself fully as to values of the various production models so that when the right gun comes along you'll know what it's worth to you and it's then easy to decide whether or not to make the offer. A collector piece is a personal thing and should be acquired because you want it and are able to place your $$ value on it. It's not what a collector piece is said to be worth that establishes the selling price, it's how much the buyer is willing to pay for it. Don't impuse buy. Sometimes a piece may be so rare that even if altered it is highly desirable - this is a rare exception. gg