Clutch Problem?

i am just begining to drive my car again and in the process, sort out the odd problem from a full grounds up restoration.
This is where i show my lack of mechanical savvy.
As part of the work i replaced my clutch with a centerforce clutch and a new flywheel.
When driving usually at the higher end of the RPM band i get a sound coming from the transmission.
Its hard to describe a sound but it not a rattle or a chain like sound. it is not loud but it is definately there. It is more like the sound of a revolving metal plate rubbing slightly against a more slowly revolving plate. Or the sound that would be made by dragging highly polished metal over sand.
The instructions on the new clutch said it would require 500 miles to break in ( i've only done 100 or so).
Gearbox oil was changed as well.
Does this sound like it is just the clutch being broken in, or a new flywheel ( if they get broken in). Or a potential major problem.

There is also perhaps a more simpler answer -when i had the car painted I had the entire interior redone. When they installed the new carpets & door panels etc they did not replace the sound deadening that was there previously. Potentially the noise was always there but not audiable due to the sound deadening.

On a related note i do have a little difficulty shifting into 4th since the restoration. I am assuming that this is because of new shift coupler bushings and a short shift kit i installed.

Any thoughts would be appreciated.

Pazz
79 SC TARGA

Maybe your clutch is slipping, try putting it in a higher gear while going slow to see if it does the same
I wouldn't be too concerned until the break in period is over