Heartthrob exhaust not sealing to manifolds

[Orion88]

I installed a manifold-back system from Heartthrob (the same kit available from JC WHitney or LMC). Had to put a dent in the passenger downpipe to get around the bellhousing. Then after I had all my pipes routed, clamped, and hung, I went to tighten my stud nuts/springs. After they bottomed out I got up and looked in the engine bay, and there were gaps where the donut seals the downpipe and the manifolds. I used the same length studs that I had on the truck initially, and the springs are even a little taller because they aren't compressed down from years of use. Has anyone else had this problem? Is it the donut seals Heartthrob sent me or is the angle wrong on my downpipes?