I've got a type 3 mx8 combo that I bought an extra top single 34" barrel with forearm for. With the type 3s they are all hand fit and some barrels will require work to fit well. The barrel I got has a bit to much head space when mounted on my receiver, and to change the lugs to fit tight would be pretty expensive. I've shot the barrel and it worked, but there is a bit too much daylight between the receiver and barrel.
You probably already know this, but I'd make sure you have the option to return any barrel if it doesn't work out.
I'm assuming you have a receiver already? As I'll never use the barrel, if you wanted to see how it fits up to your receiver I could send it to you (I'm in Minneapolis area)and if it works send a check, if not ship it back. I paid $900 for it which is what I'd want. If it's something you're interested in let me know and I can send an email or give you a call.