it needs to be line honed also,
with the 2 middle studs on each main cap
(3 center main caps) torqued down in place
if you go with a girdle, it's part of the girdles' support
IMO It can't hurt, if your budget can handle it
it's not that expensive either,
IMO cheap insurance
(unless you have a good aftermarket block, that was designed for
& came with 4 or 6 bolt main-caps)
It just helps, to tie 'all the bottom end together'
the block, sides/oil pan-rails & mains
so the main studs/main bolts aren't acting
'like a flag pole, waving in the wind'
the weakest part of an RB block,
especially an OE factory 2 bolt main block
is the 'main journal webs' undercuts just above the mains