Can you put a glass pack on a go kart?

Can you put a glass pack on a go kart?
Yes.

Its debatable if it will improve the output of the motor, but you can pretty much put any type of muffler on a go kart. Think of the components in separate sections: engine, exhaust pipe, muffler.

Factors to consider:
1) Will each of the components mate up to each other? If the exhaust pipe is 1" in diameter, and the muffler is 2" (like from a motorcycle), then you'll need to work out how to mate the two. This can be done with a reducing or enlarging adapter or by tapering the larger end.

2) Will it fall off? You'll want to wonder if mounting brackets or straps will be needed to keep everything together.

3) Will the carburetor need to be adjusted? Changes in exhaust pipes and mufflers may require carburetor adjustments to the fuel/air mix or to the jetting.

4) 4 stroke or 2 stroke engine? 2 stroke engines gain a lot of power based on the exhaust pipe shape (enlargements and restrictions). the muffler, being a restrictor, could affect the output. Though smaller 4 strokes look for a little backpressure from the exhuast and muffler, swapping mufflers isn't too much of a issue.