I have a noise, a slight rattle, at full throttle/load at high RPM. I currently believe it is something loose inside the muffler. Does anyone have a muffler I can borrower/rent in So Cal to put on and see if the rattle goes away?

I am likely to buy the new replacement from Porsche. But before I do that, I was hoping to test my current one. So any muffler that fits a 1973 911 will do - I believe all mufflers 65-73 will work. Or, if it is inexpensive enough, I supposed I could buy it too.