If you're going down the welding route then you'll need to cut the join and weld a sleeve in place, or we can help with a new replacement exhaust system...
We've just done a set of Grids in 19" for a GT4 owner, if it's 5 spoke you're after then the 19" GTR wheels we do have a few colour options available...
Simon, ironically the same setup as yours including the exhaust system went through the emissions with no issues at all, he's also got the UpRev too...