As rickmg says, you can isolate an area of noise quite easily just by listening to various points around the engine. My favorite listening stick is a long screwdriver, handle to my ear, works great.
Manifold gaskets can be difficult to seal on these motors. I've found intake leaks by spraying Berrymans Chemtool around manifold with engine running, if she speeds up you've lost your intake seal.

Best of luck.

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed