Classic & Vintage - derailleur compatability

Hello all.

I have a bike (about '84) that my father put together for me many years ago. I've been cleaning it up and have upgraded a few parts to convert it to a nice commuter.

Right now it has a beaten up Campy Velox rear derailleur on it, friction shifting. The levers are on the headtube.

I'd like to upgrade the rear derailleur if possible. What do I need to know about finding a compatible derailleur? I know that's pretty vague, but as this bike was put together with various parts, I can't tell you the groupset, etc.

If I wanted to stick with friction shifting, would there be a good bet that any derailleur of this era would work with my cassette (which I believe is 6 or 7-speed)? Any suggestions for a brand/model that would be good to look at?

What about if I wanted to upgrade to indexed shifting? Is that possible or advisable? I can deal with friction shifting if it makes finding a replacement part easier.

Thanks. If you guys need to know any more details, let me know. I can take a picture if that helps.

Pictures are always good.

When you say head tube, do you mean handlebar stem? Does the bike have a dérailleur hanger on the drop out? Is it really a cassette, or a freewheel? Can you count the cogs, 6 or 7? Is there a brand stamped on them?

I could go on with questions, but you get the idea.

Need more information if you want help.

Oh, and pictures of what you want to change or have questions about.

The Campagnolo Velox was a shinier version of the Valentino which existed only so the manufacturer could say the bike had Campagnolo! They're not very good. A Gran Sport, Nuovo Record, Nouvo Gran Record or such would be a nice replacement, or a Suntour Cyclone if you don't feel the need to keep it all European.

The front is probably the boxy Valentino, not much reason to keep that either, match to what you find for the rear.

Typically all friction stuff is pretty interchangeable.

If you want to go index, that is more complicated as the levers and rear derailler will need to be somewhat of a match for that to work. These systems work best when the rear DR is same brand/model as your shift levers, such as Suntour 3000, etc.