An HDTV receiver box to insert in vintage TV IF strip?

[MRX37]

To me that would seem difficult to pull off, and would essentally turn the TV into a hybrid between old and new. While that would be pretty cool, my main concern is how well the new would get along with the old...

In my opinion, an HDTV box combined with a wireless transmitter hooked to it's output would do the same job, and you wouldn't have to modify the TV.