66' 273 Knocking/Ticking

The 273 in my Valiant has less than 1000 miles on the rebuild (I purchased the car after the rebuild), but the engine has a slight ticking to it. I thought it could be an exhaust leak I installed new gaskets (which helped) but it did not resolve the issue. A mechanic told me that its the rocker arms, and that they need to be replaced, but the engine has the older style rocker arms, can these be adjusted, and if so how hard is it? Any advice would be helpful. Thanks!!!