Peacock's side head into the match knowing that a victory would be enough to seal the title in the Football Association's annual four-team tournament.
Portugal were beaten by Turkey at Sincil Bank on Friday night, but looked classy as they defeated Australia 4-3 in North Lincolnshire earlier in the week.
"The Portuguese are always strong in terms of having quality outfits," said Peacock.
"They always seem to get to the European finals and do very well. I felt Turkey were a good side and they are always very strong as well. They managed to beat Portugal 3-2, so I think it is all set up nicely.
"The bottom line is that we are going to try perform well. We've managed to rotate the players around which has been great. We'll wait and see what Sunday brings but it should be a very exciting game."
Peacock is a former Scunthorpe player - making 220 appearances in the 1970s - and brought the team to Glanford Park on Saturday to watch the Iron outclass Crystal Palace 3-0.
While the crowd on Sunday will not match the 5,292 that watched that match, Peacock is hoping for something similar to the crowd of more than 2,000 that watched them defeat Australia 4-0 at Blundell Park on Friday night.
"It's nice for the lads to play in these sort of environments at traditional football grounds like Blundell Park," he said.
"Having 2,000 there was a real big boost for them. We've been well supported and hopefully we can get a similar size crowd on Sunday. So far we've enjoyed every minute of the tournament."
England top the table, ahead of Turkey on goal difference, but would expect to be overtaken if they do not manage to beat Portugal.
They could still win the tournament if they are held to a draw, but would rely on Turkey and Australia also playing out a stalemate in their match at Blundell Park.
The match kicks-off at Glanford Park at 3pm, with entrance £3.