Engine painting

So I ran the motor on an run stand prior to installation. Things went great and it’s ready for paint. In the past I’ve painted the balancer, tchain cover and back of the wp housing before mounting the wp housing. The question is... should I remove these parts for full coverage or would it be more correct to paint with parts in place knowing paint won’t reach everywhere? I’ve never really paid attention or questioned how original cars look.

Thanks,
Sandy
‘70 Hemi RR, B5, 4spd

Factory didn't spend any time or much care, and painted those installed.
Me, I like to paint the backsides & hidden areas, assemble, then paint the outside complete in the OEM scheme.
I also prime everything after cleaning it to death. Factory didn't do that, though. Nor were they real shiny, more like a semi-gloss.
Every one of them I've done over the last 40 years still looks great, though I do keep them clean & leak-free.
Dead-nuts correct is to paint it like the factory did, a quick hosing with paint with no regard to longevity.