FAT-451

See if you can get a socket - slightly smaller than that pesky nut and belt it on with one of your big hammers.  then you should be able to just ratchet it off.
 
Failing that what ^^^^^^ said.

milzy here...cbf changing accounts
 
thats pretty much it, although most people just weld onto their existing housing instead of buying a new housing.
 
As for welding a cast housing, I have done a couple and haven't had any issues. Basically just preheat the housing and weld it while its hot. They say you should let it cool in sand bla bla, but ive just let it cool naturally and haven't had any issues.

You can always block off that wastegate and just run a pipe/wastegate off the turbine housing. Will control boost better then off the manifold.

That's a good cast unit but most do it like this
 

Pump up the spare tyre