I'm confused about any difference of the 273 vs. the rest of the LA heads. When I look up part numbers on Summit or JEGS for the Charger and the Cuda with the small blocks, the part numbers are the same?
The Magnum heads are distinguished from the older LA heads by their pedestal mounted rocker arms (like the Chevrolet engines). The older LA use a rocker arm shaft.
The 273 and 318 (except the factory 318 4bbl) use what can be considered small port heads. The valves as well as the passage ways in the heads are smaller than they are on the 318 4bbl, 340, and 360. The latter can be considered large port heads.
The differences in passage ways are not so much that mix and match among them is impossible. For instance, the Eddy Performer RPM intake is designed for the large port heads. It will fit on a small port head, but the alignment of the manifold with the cylinder head will be off. A better choice for an intake manifold might be an Eddy Performer, Weiand Action+, or a Weiand Stealth. All of these are designed for the smaller port head.
There is even less difference in the exhaust passages. The challenge with headers on the A-body is finding something that fits the driver's side without a lot of cursing and banging. If your car has power steering, the list of headers that will fit is short. As long as a factory head is used, it doesn't matter which LA engine it is on.
