273 is it good engine?

The 273 is best for keeping it factory. My 1965 Dart has a 273 (avatar) and my 1964 Valiant a 225 slant, and keeping both that way. You'll probably get more lookers at a car show today with a slant, especially if you add mod's like the large Hurricane intake or a turbocharger. If you really want a V-8 for more power, the 5.9L Magnum (360 cu in) is probably better since common and upgrade parts available cheaper. That gives you modern spark, MPFI, roller lifters, and better transmission with overdrive and lockup. If you can't manage installing a high-pressure fuel pump and regulators, you can get a manifold to use a carburetor on a 5.9L. The biggest downside is the heads are prone to crack. You must strategically dent the oil pan to clear early-A steering, plus need the V-8 cross-link which drops lower to clear a V-8 pan (even a 273). If a 5.2L Magnum (318 cu in), I think you can fit an early 273 oil pan to clear the steering. Some (all?) 1966 slant cars had the V-8 cross-link. Like most smaller displacement engines, the 273 spins higher, which is what you must to do access peak power. A few have installed a modern Hemi engine and tranny, but a higher threshold and I read those engines have some issues.