hittman..

 

i have an 03 uktra classic
this may sound wierd but can you block off the left header and use the crossover as the header for a 2 into 1 exhaust, and what would be the result

 

Welcome to the Forum!
Rather than block it off, you would want to get or build a header for your purpose, especially if you have any performance work done. If the left side is blocked off, you may end up with an issue where the air doesn't flow well, but swirls in the blocked pocket. The more air into the motor, the more room you need to get it out. Better choice is true duals.