There are a total of 8 items to collect that once belonged to Johnny Silverhands. You need to collect all of these items in order to get the "Breathtaking" Trophy, which is for collecting all items that once belonged to Johnny Silverhand.
► All items that once belonged to Johnny Silverhand:
Johnny's Dog Tags 0:00 (Obtained automatically during the main job - Tapeworm)
Johnny's Tank Top 0:22 (Obtained automatically once completed the main job - Tapeworm)
Johnny's Aviators 0:43 (Obtained automatically during the side job - Chippin' In)
Johnny's Samurai Jacket 1:07 (Obtained automatically during the side job - Chippin' In)
Johnny's Malorian Arms 3516 1:35 (Obtained during the side job - Chippin' In)
Johnny's Porsche 911 1:51 (Obtained during the side job - Chippin' In)
Johnny's Dog Pants 3:31 (Obtained by looting the travel bag during the gig - Pyschofan)
Johnny's Dog Shoes 4:10 (Obtained by looting the locker during the gig - Family Heirloom)