New-old guy needs to know

the common reason I'm leaking coolant where the intake hits the head? The engine is a 89 350 TPI from a Corvette, alloy heads. I have no history on this engine before I got it, 5 years ago, and put it into a 85 XJS. Also what are the best intake gaskets? Factory or aftermarket? I'm just glad it's an external leak and not in my oil.
Thanks Much

Fel-pro gaskets! The lower section of the TPI manifold should seat flush with the heads, I would check the to see if the water passages are lining up, sometimes people put vortec manifolds on old version heads and vice-versa, just my 2 cents.