'55charliebird. GooD point that the 'Bird aluminum valve covers, which were optional all three years, required longer valve cover studs. Likely the studs are available from all of the usual 'Bird supply vendors. I noticed them recently at Mac's, too.
Perhaps, the previous mechanic secured the acorn nuts on the end of each stud then fed the assembly through the valve cover and into the rocker arm bracket to accomplish making it just long enough to secure into the cylinder head? I'm speculating, and assuming that you have the optional 'Bird-only dress-up kit aluminum valve covers.
Isn't working on this old stuff fun!?!
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York