Any gains adding 1.6 rockers to stock 273?

You will get some benefit in torque, something along the line of putting a "RV" cam in. You will pick up a slight amount of duration at 0.050" lift along with the almost 0.030" lift. The duration will not produce much, but the added lift on a low lift cam will be a benefit. Now you do not want to expect miracles. What is your installed valve spring height. If it is about 1.800" you could get beehive springs to aid valve control. The extra rocker ratio stresses valve control a bit due to the faster valve opening travel speed. Depends on how hard you intend to run it.
Down the road if you need to touch up.the valve seal, you could look to Magnum or LS valves. Larger valve diameters with smaller valve stems.
Ignore the NA SAYERS on here. Too many that are more race oriented and nothing is good enough until it is too much. As long as valve to piston clearance is good there is nothing but benefit.
I would be very cautious about stuff that is cheap. These days you do not seem to be able to trust expensive parts either, but you get more or less what you pay for. Look for American manufactured. Too much Chinese **** is just that, reconstituted Yak turds.