250 engine details

[TLea]

good morning. new to forum just introduced myself. Working on 66 C 20 w/250 restoring to as new (concours). I'm trying to understand how engines were painted. There is a thread here with a beautifully restored 250 and all the fasteners are plated suggesting bolt ons (valve cover, timing cover, side covers, oil pan, intake etc) were painted before engine was assembled. I'm used to most makes painting engines with most common pieces assembled. Which is correct?
Thanks in advance.
ps: This engine was never repainted but someone had been inside so gaskets all changed however the balancer clearly had original turquoise paint on it