Wilson said, "This was our most difficult selection to date, with a number of other players also deserving of starting places. Owen Jenkins for example has performed very well but we felt that Jordan and Hallam had made a big impact in the games, both when in the starting line-up and from the bench with their running lines and creating and scoring tries so we wanted to get them both on the pitch, while Ashley Evans has been extremely consistent.
"A lot of consistency has been shown throughout the side, with the all the back line raising their game during the tournament which is credit to the players and to Byron Hayward, our attack coach. Steffan Hughes has been a real solid number in midfield and has formed a good relationship with Jack Dixon. The half backs too are growing with each game,
Sam Davies probably had the best 40 minutes I've seen him play in the first half against Argentina.
"Our forward pack put a huge amount of work in on Thursday and will need to front up again against a physical set of South African forwards."
After reaching the last four last season, Wilson and his charges are determined to go further this time around.
"We've had a good look at South Africa now. They are similar to their senior side in that they have a heavy pack but they also have an extremely dangerous back three which we will need to be wary of.
"We are pleased that we have achieved the goal we set out for ourselves at the start which was to reach the semis but we are far from finished. This is a game we can realistically win and reach the final. That would be a huge achievement but something we are targeting now."
Wales Under 20 v South Africa:
Jordan Williams (Scarlets / Llanelli); Ashley Evans (Ospreys/ Bridgend), Steffan Hughes (Scarlets / Llanelli), Jack Dixon (Dragons), Hallam Amos (Dragons/ Newport); Sam Davies (Ospreys / Swansea), Rhodri Williams (Scarlets/ Llandovery); Gareth Thomas (Scarlets/ Carmarthen Quins), Ethan Lewis (Blues / Cardiff), Nicky Thomas (Ospreys / Swansea), Carwyn Jones (Scarlets/ Carmarthen), Rhodri Hughes (Ospreys/ Swansea), Sion Bennett (Scarlets/ Carmarthen), Ellis Jenkins (capt, Blues / Cardiff), Ieuan Jones (Dragons/ Newport).
Replacements: Elliot Dee (Dragons / Bedwas), Thomas Davies (Blues /Cardiff), Dan Suter (Ospreys/ Bridgend), Jack Jones (Ospreys / Rovigo), Daniel Thomas (Scarlets/ Llanelli), Joshua Davies (Dragons / Bedwas), Aaron Warren (Llandovery), Thomas Pascoe (Blues / Pontypridd)