This should be the new style 3500 header flange..

http://60degreev6.com/store/index.ph...d&productId=63

The new 3500 stuff and 3900 stuff is identical as i remember.

mounting is different don't think they will work........

Then you have the original style 3500? That should be the same as the 3400.

somewhat the same, they are pretty close but i sold my TOGs and want to go with custom headers and having flanges to start would sure make my life easier......