Hey Brent, I use a high temp silicon sealant with copper in it.
Buy Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker (3 oz) 81878 at Advance Auto Parts
You should have a mechanical fit that is very close and be able to seal it from there. I also have been using little welded on tabs that you can pull the slip joints together with a couple of small bolts. I'll try and find a picture.