Ospreys prop Jones has been struggling with a toe injury, while Halfpenny (ankle) and Byrne (knee) have also been fitness concerns with Wales' opening World Cup contest against South Africa less than four weeks away.
The return of tighthead Jones will be a particular boost as the Welsh scrum found itself in strife during the back-to-back fixtures against England, and is likely to face a tough examination against the Pumas, as well as against the Springboks on September 11.
But coach Warren Gatland has had to wait over the fitness of a further quartet of players ahead of this weekend's final World Cup warm-up game.
Gethin Jenkins, Ryan Jones, Stephen Jones and Rhys Priestland (all calf) were put through their paces as they sought to prove their availability.
The injury to Jenkins would appear to be the most worrying as the Cardiff Blues prop has struggled with calf issues over the last two seasons, and has not featured for Wales since last autumn's defeat to New Zealand.
Wales' were also dealt a major blow yesterday when captain Matthew Rees was ruled out of the tournament as he needs surgery on a persistent neck injury, and joins full-back Morgan Stoddart (broken leg) in being ruled out of the global showpiece.
And assistant coach Shaun Edwards revealed that the pain that Rees was experiencing due to his injury made the decision for him to have an operation an easy one.
He said: "From a rugby point of view it is incredibly disappointing to lose your captain but there are more important things in life than rugby, and he is in such pain it has to come second to his life.
"Matthew normally has a bit of banter and a joke but he is not like himself because he is in such pain.
"You have to take the doctor's opinion and get it done because you can't live your life like that.
"We are gutted he is not leading us at the Rugby World Cup but it will be good to see him back leading a normal life without pain.
"He can't sleep and he is in constant agony."
Centre Gavin Henson is another who may yet experience World Cup heartache as the dislocated bone in his wrist is set to sideline him for six to eight weeks, although Wales have not ruled out taking him to New Zealand to feature in the latter stages.
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