Sounds like you need a barrel and stock. For that money I'd buy another shotgun.
I have a Mossberg 835 that I use for shooting skeet. It's about all I can use it for being it's built as a turkey gun and is way too long for a HD gun.
It's funny because I went looking to change it around and make it into a HD gun but the 835 is next to impossible to find parts for if HD is your goal so I was looking at getting a 500.
I understand you wanting to shoot clays. It sure is a lot of fun!