OK, update: turns out that, unbeknownst to me, that the 270 head comes in small port and large port versions. Mine is a small port, and the engine had a large port gasket that leaked like a sieve. I had to hunt a little for a gasket specific to small intake ports, and found them available from Larrow & Sons in Sandy, OR. I also bought some of their manifold studs, which use a finer machine thread than the stick studs, and the manifold is now tight - engine runs smoothly.
Thanks!
