Removing the dipstick housing....

The new (to me) engine that is going in my '84 300D needed a new o-ring for the dipstick housing, and apparently needs a new dipstick housing. I want to pull the housing from my old engine, but it is in there pretty firm. Does anyone have any tricks? I was thinking vice grips, but I don't want to deform the tube. BTW, I have pulled the fuel filter housing and IP, so I have pretty good access.