Vintage cabinet with newer chassis?

oh,believe me,i totally understand your guys' thoughts on gutting a set just for the outside of it.i believe that if something can be salvaged then by all means tinker with it till it's fixed (hell, even the "new" engine in my chevy is still a ' 68!),but i'm sure there are a few junky ones out there that could stand to be completley replaced (hey it beats staring into a black box like has been said before) i'm aware of the differences in the actual tube sizes and am willing to give up some of the size of the screen (slightly larger screen behind smaller opening) as long as it's something i can work on and customize to make my own.the only reason i'm even asking about replacing it with a newer set inside is because i know the odds of finding a cheap,working original set are next to impossible for me,or at least have been so far.if i can find one that's cheap and works,i'll probably keep using it until it WONT work any more,but if that's not possible,i'd still rather look at something old rather than new.once again,thanks for your time,as i'm sure i'm rambling.
-frank