What Simon said;
PLUS:
I've noticed that replacement cylinder head studs are often on the short side of ideal. In which case, the 5 x head nuts are often only held on by say 3 to 5 threads at the top of each stud. Not Good. Putting a washer below the nut, although good engineering practice, makes this problem even worse. Just something to watch-out for. No two engines are the same. Proceed with caution and good judgement....
Of course, longer studs would be great - but, if too long, then you will likely run in to problems getting the cylinder head off with the engine still in the frame! Something else to watch-out for....!
Peter B
Bristol, UK.
P.S. Definitely use washers on alloy heads!