TSO vs Non TSO instruments

I would like to replace the vertical speed indicator and the directional gyro. Is it legal to replace them with non-TSO'd instruments for my 1951 Pacer (much cheaper)? From what I've read, it seems there is no definitive answer. People's opinions are all over the place. Has anyone had any experience with just adjusting them and cleaning them instead of replacing them? Thanks in advance for anyone's insight.

What I have always understood was that required instruments in a certified airplane needed to be TSO'd. However my Clipper's original instruments had no TSO. What about getting your instruments overhauled vs replaced?