Weld the hole on the exhaust pipe shut. As long as the EGR is disconnected, the other end doesn't matter. When I rigged up a Renix exhaust manifold on my '84 wagon years ago, I used the Eagle egr top part of the pipe and connected it to the Renix pipe with a compression tube connector and minor bending because it still had to go through emissions.
Speaking of Triumphs, I had a Bonneville turbo for about a week. Got it from my uncle who rebuilt it in our basement but he didn't have the timing right. He went to kick start and it threw him upwards so he broke his shoulder on the floor joist above, came back down, kicked again and broke his foot!
I got it right and was breaking it in when I was run off the road by some yahoos (intentionally). Bike hit a tree and caught fire. I was lucky enough to hit a mud filled ditch at about 60 mph. Never did find them again and I guess it's a good thing.