Toshack's squad comes mostly from the Coca Cola League with just a few current Premiership players. The match will be played in Luxembourg City next Wednesday March 26th, ko 20:15 local time.
Keeper Wayne Hennessey and defender Chris Gunter will drop from the senior squad to assist the U21's in their crucial qualifying game in Bosnia on the same day.
"I spoke with Wayne when we were together for the Norway game to explain what my thinking was and similar with Chris," said manager John Toshack.
"This is such an important game for the Under-21s because they have put themselves in a position where they can do something that they've never done before.
"Qualifying for the finals in Sweden in 2009 has become a real possibility and if they do get there, all these lads can go.
"The two teams travel together and we get dropped off in Luxembourg and the Under-21s carry on to Bosnia and there could be changes either way."
Myhill, an American, qualifies for Wales through his mother.
"(Boaz) is playing regularly in a side who are doing very, very well," continued Toshack.
"This game is one we've decided on having a look at a number of new players and he's one of them."
The full squad is.
Boaz Myhill (Hull City), Lewis Price (Derby County), Richard Duffy (Portsmouth), Neal Eardley (Oldham Athletic), Craig Morgan (Peterborough United), Lewin Nyatanga (Derby County - Loan Barnsley), Sam Ricketts (Hull City), Stephen Roberts (Doncaster Rovers), Ashley Williams (Stockport County), Andrew Crofts (Gillingham), Arron Davies (Nottingham Forest), Simon Davies (Fulham), David Edwards (Wolverhampton Wanderers), Carl Fletcher (Crystal Palace), Owain Tudur Jones (Swansea City), Jason Koumas (Wigan Athletic), Joe Ledley (Cardiff City), Brian Stock (Doncaster Rovers), David Cotterill (Wigan Athletic), Jermaine Easter (Plymouth Argyle), Freddy Eastwood (Wolverhampton Wanderers), Daniel Nardiello (Barnsley)