What can I use to seal Slant Six intake/exhaust manifold?

[WH23G3G]

So I'm sure someone here has done some Slant Six work. I've got that Plymouth Valiant 1965 with a 170 which had an intake gasket leaking. So I changed it out and now the exhaust is leaking right where the intake bolts ontop of the manifold where the two manifold connect. The exhaust/intake combination gasket is good and not leaking. The gasket that is leaking it the three bolt hole metal gasket between the two manifolds. I didn't use any kind of sealant on it. But if anything will make it seal good, I'll retry it. What if anything can you recommend? I think if I can get that to seal it should be running smooth and then I can try to add my swapped over original A/c compressor and brackets.

[rt green]

machine shop. have them square them up