Big end nuts

[Charles P]

I was prepared to turn down the camshaft between the lobes but I’d need to take a lot off to clear the cap heads.  So I’ve ordered some button head “bolts” which are actually “set screws”.  I may be able to get away without turning down the camshaft.

Turning down the camshaft is not a good idea.
Button head cap screws are a decent idea but as you say, set screws. 
Low head socket socket caps may save your day and are available in normal bolt style.
See page 26
https://www.holo-krome.com/uploads/7/2/7...g_2018.pdf
(opens big PDF so don't do it on your phone. )

And if I'm putting a socket head inside an engine I make sure it's Holo-Krome or Unbrako. Beware of some EBay vendors being fast and loose with the term "Unbrako"