A 273 is weak to begin with. Adding ever so slightly increased duration and lift won't amount to anything perceptible. Total waste of time and money imo.
Too many folks trying to forge different paths. But there's no shortcuts to power.
Get some headers, an improved intake, a 4bl carb, some upgraded valvesprings, and a mild cam. It'll be a significant improvement.
If you're crafty with your shopping it won't cost that much more than those 1.6 rockers.