Carter "X" fuel pump question

Hi Guys;

I've been fussing with my '68 GT500 lately and got a question.

The other day I had the Shelby idling, I felt the fuel pump from above the power steering pump and it was noticable knocking within.

What's regarded as normal internal movement in relation to the cam eccentric? I understand the need to move in order to pump the fuel but could it be excessive to the point of noticable if felt?

The engine is a 428SCJ with about 10,000 miles. I did not build the engine, just maintained the beast.

Are they rebuildable with a obtainable kit or know somebody who specializes?

Any thoughts???

Thanks;

Tool