Exhaust change

Hey all, last time I posted on here I was driving myself to a early grave due to my 1989 golf cabby been a complete a**e! However since then iv managed to fix it and apart from the swimming pool in my spare wheel hole it's running as a beautiful daily runner been out with the roof down for the last few days and have spent the entire time grinning  however been a young male and really want to hear the engine more so iv decided to change to the exhaust to stop it wining to much and make it a low grumble…. I want to buy a cherry bomb rear box however my question for you guys……. Does anyone of you know what size cherry bomb I will need?  If anyone has put a cherry bomb onto the golf cabby I will be very grateful for any help thankyou all