273 Rocker on 340

Did it on several cars. As far back as 1974.Big thing to look for is valve spring clearance as performance springs may be larger diameter compared to the spindly 273 spring. We would grind some from the back of each rocker to clear the retainer and spring. Easy to do. 318-340-360. They work well,along with the stock 273 ball and cup push rods.
We ran the Crane Hyd with a .490 lift and the Mopar Performance purple shaft .508