Vintage Bikes - I don't fully understand what you are trying to accomplish. I don't know what SC & DJ mean or belt wrap. If you want to replace your serpentine belt, idler pulleys and belt tensioner pulley you should buy the correct part numbers for your engine. The belt tensioner pulley is designed to put lots of tension on the belt. Before you can remove the belt the belt tensioner tension has to be released. The following you tube link demonstrates how this is done on a MB 3.2Liter engine . Using a breaker bar or long handle socket bar, the tension pulley is rotated to release the belt tension and allow installing a pin to temporarily lock it in the release position. The pin needs to be at least 1/8" dia or can be an allen wrench. The video shows how to install the pin which needs to be fully inserted in the hole on the tensioner. If you buy a new tensioner pulley it comes with a pin installed which gets removed after installing the belt. If your engine has high mileage, I highly recommend replacing the idler pulleys, belt tensioner pulley, and the serpentine belt.
Good success