In case anyone was wondering it appears A th400 will fit with the on3 fox kit. I am using an advanced adapters kit so it is not the same as the JW bell. I have the on3 y pipe also. I took measurements as best I could before I started and it appeared everything would work. Here is a pic of the fit up. The downpipe is only sitting in place and not actually bolted up but it will fit. I did trim just a little bit of the ear that sticks out on the th400.