Extra terracing means the ground's capacity for the match has gone up by more than 500 to 6,533 for a mouth-watering encounter which sees undefeated Wales take on second placed England.
A win for Danny Wilson's side would mean a first Grand Slam for a Welsh Under 20 side, and first at this level since Wales Under 21 secured a clean sweep in 2005.
Wales Under 20 head coach Wilson has made four changes to the side that beat Scotland 42-17 last Friday with Dragons centre Jack Dixon making his first start of the campaign, partnering Cory Allen, while Ashley Evans returns on the left wing in place of Aaron Warren who misses out through injury. Up front, prop Nicky Smith and hooker Elliot Dee get the nod to start in the front row with Nicky Thomas.
Wilson said, "We are of course pleased with the way this tournament has panned out for us, playing England for the chance of winning the Six Nations and Grand Slam is a fantastic opportunity for these players ahead of the Junior World Championship in June.
"We have matured as a squad during the tournament, but we will have to sharpen up in a number of areas if we are to beat England on Friday. Our discipline especially must improve - we can't give away penalties and yellow cards to a side like England and expect to come away with a result.
"It's brilliant to know we will be playing in front of a sell-out crowd. The support at Eirias has been superb for every one of our games, the backing gives the players a real boost and could really make a difference on Friday."
Cllr Graham Rees, Conwy's Cabinet Member for Tourism, Marketing & Leisure said, "Having a sell-out Wales Under 20 match at Eirias is absolutely fantastic news - it promises to be yet another fantastic evening of sport. The atmosphere at Eirias is brilliant so a huge thanks to the public in North Wales for showing their support for the next generation of Welsh rugby stars."
Wales Under 20 team v England (Eirias, Colwyn Bay, Friday 15 March, 7.35pm, S4C):
Jordan Williams (Scarlets/ Llanelli); Harry Robinson (Blues), Cory Allen (Blues / Cardiff), Jack Dixon (Dragons), Ashley Evans (Ospreys/ Bridgend); Sam Davies (Ospreys / Swansea), Rhodri Williams (Scarlets/ Llandovery); Nicky Smith (Ospreys / Swansea), Elliot Dee (Bedwas), Nicky Thomas (Ospreys / Swansea), Carwyn Jones (Scarlets/ Carmarthen), Rhodri Hughes (Ospreys/ Swansea), Ellis Jenkins (capt, Blues / Cardiff), Daniel Thomas (Scarlets / Llanelli), Ieuan Jones (Dragons)
Replacements: Ethan Lewis (Blues / Cardiff), Gareth Thomas (Scarlets / Carmarthen), Dan Suter (Ospreys / Bridgend), Jack Jones (Ospreys / Rovigo), Sion Bennett (Scarlets/ Carmarthen), Joshua Davies (Dragons / Bedwas), Hallam Amos (Dragons), Steffan Hughes (Scarlets / Llanelli)