How to remove slip hub / flange 1970 3/4 bath

[silversafari]

Hi, I'm trying to remove my black water tank on my 23' 1970 Safari to work on floor and tank repairs/replacement. The only thing from keeping me from removing the tank is this Thetford slip hub from the dump valve. It was clamped on with a pipe clamp which I was able to remove. It won't pull loose, should I use a heat gun? Should I keep pulling and twisting? Any tricks would be appreciated.

thanks,
Brian

[silversafari]

After some twisting, tugging, and pulling it finally came out.

[Colin H]

Any "treasures" come with it?
Colin