Best foot forward in training.
Leinster duo McGrath and Moore are primed for bench duty in Sunday's RBS 6 Nations opener against Scotland in Dublin.
Fast-developing tighthead Moore is expected to win his first cap as a replacement, with experienced campaigners Cian Healy and Mike Ross Ireland's starting props.
Ulster hooker Best will win his 71st cap, with Sean Cronin among the replacements and McGrath in line for just his fourth international outing if he joins the fray.
Best admitted Ireland's forwards have sunk their teeth into some testing scrum tussles in training at their Carton House base in Six Nations preparations.
"When we're training in the scrum now, if you don't get it right you're going to get done, which is exactly what it will be like on Sunday," said 31-year-old Best.
"And that's important. It obviously brings competition for places, which is good for everyone, with young guys coming through."