can anyone tell me how it would be possible to install a flowmaster muffler on a '91 vert?

 

At the risk of sounding rude, why would you want to? Got one sitting around somewhere or something?

 

I don't see why not. it is far enough from the motor that heat shouldn't kill it too fast. I am not sure of what it will sound like though. Remember our engines sound nothing like pisston motors with the same mufflers on them.