66 Barracuda 273 Intake Manifold options?

In 50 years I have never replaced an intake for a stat-house leak...... But I tend to run 7psi caps, the Heater-cores and hoses last so much longer; decades, and sometimes several decades even.

Get a fat aluminum housing and file it flat. Make sure the receiver step for the stat is deep enough. I install studs into the manifold, with fine-thread up top, then use the load-spreading washers from the slanty intake/exhaust manifold applications, and fine-thread nuts.
Done as above with a 7psi cap, I have used greased Cornflakes cardboard for a gasket.
I wouldn't give a nickle for the steel stat-housings.