Set it on without gaskets, it should seat on both intake surfaces and the valley at the same time if there is no major milling of the head intake surfaces. For example if you take a b/blk chevy manifold without gaskets on a stock short deck you can hardly get a .010 feller gauge under any surface. I just did this with a Hilborn stacks injection unit to make sure the injection unit hadn't been modified.
Zip.