273 were interference adjuster, meaning there is a mean drag on the adjuster so it doesnt back off under its own load (supposedly, the thread pitch wears over time). The more you mess with it, the looser the adjusters get, so the locknuts are a good measure. IIRC, the stock adjusters were hollow hex heads and the after market were slots. Allen head would be the best, put a ball end in there on a spring loaded telescoping T-handle and you could adjust them while they are running without the T-handle jumping around. Hey, thats my million doller idea!
