Never saw this thread originally, but a guest was viewing it and I happened to notice.
273s are great little engines that like to wind due to their lightweight reciprocating weight. I've seen a stock-bore 273 run in the 10s (the bore being about the only thing stock, along with the steel crank). Most of them have steel cranks that can be rebalanced for use in 318/340 applications. A friend of mine threw a stock '70s-era 360 four-barrel intake/carb combo and dual exhaust at his otherwise-stock '67 Dart GT two-barrel engine, and we had a lot of fun with it. It was surprisingly quick. He didn't win every race, but he won more than I'd have expected.
On the downside, they're basically identical to all the other LA engines bottom-end wise and give up 45 cubes to even the under-respected 318. As with the '70-down 318, they use lightweight rods (meaning weak, not some sort of sneaky race part) and absolute crap cylinder heads--even the most-restrictive smog-era open-chamber LA head outflows them considerably.
A high-compression 273 Commando engine makes a really nice street engine with later 340/360 heads (1.88" intakes--2.02" valves absolutely require a bore notch) along with a stock 340 cam, especially if you can get a '68 4-speed grind. The open-chamber heads not only flow far better, but will lower the compression to crap 87-octane pump-gas territory. Of course, you could throw all the same parts at a '71-up 318 and probably make 25-40 more horsepower, even considering the lower compression.
I lump the 273 in with the 350, 361, 383, 413 and 426W engines. More cubes=more power, so if you need one of those erstwhile boat anchors for your restoration or are out to prove a point by all means get one. If you're trying to make power, move up.to a 318/340/360 (I mention the 318 only because 340s are getting hard to find, and the 360 is sort of its own breed with the long-stroke 3.58" crank that was never forged steel from the factory). In the case of the low-deck motors, the 400 is the only block to have, and in the case of the RB engines, the 440 fits that bill.
I have no idea why I wasted this much time on a thread over four years old, yet I feel good about it.
