In defense of old trim: In my house which was built around 1960, the clamshell moldings I have taken down are way thicker than the stuff I can replace it with. Much rounder profile too. If you have the time and the patience, you can be proud of the restoration on the old trim, but most of your friends won't notice. It's all about how you will feel when looking at it.
Just because I was cheap I found a house the same age as my fixer upper that was do for demo and selvaged all the molding. As soon as the neighbours heard of it I had several who needed a peice of this or that.