Joseph has made three changes to the starting XV from last week's win over the Chiefs.
King replaces big prop David Te Moana, who struggled at scrum time, Robbie Robinson will start at first five-eighth in place of the injured Lima Sopoaga, and Siale Piutau gets his first start of the season coming in for James Paterson on the right wing.
The bench has four changes, with hooker Brayden Mitchell replacing Mahroni Schwalger, who is still nursing a sore shoulder. Donnelly comes in for Joe Tuineau, who did not fly to South Africa, and veteran first five-eighth Tony Brown returns to the Highlanders.
Young winger Telusa Veainu will get his first chance to get some playing time.
Joseph said the players had taken a couple of days to adjust themselves to South African conditions after the long flight, with just one full training run, and playing at altitude at Loftus Versfeld would mean the bench would be important.
But coming off two straight victories, and gunning for a third, Joseph said the pressure was all on the home team.
"They are the defending champions while we came 12th last year. But they are the best team in the competition. They talk about the Crusaders being the benchmark but this team beat those guys last year," Joseph said.
The Highlanders have shown a strong defence in their first two games but going to Loftus Versfeld and pinning hopes on tackling everything that moved would not work, Joseph said.
"To me, the attack is more important. You can't win games from tackling people all the time. You've got to get out there and create chances.
"You look at the Bulls and they've got heaps of internationals right through their side which when compared to our team is completely different. But they won't know who we are, what we are about."
Joseph said Te Moana had struggled in the game last week against the Chiefs, so King got his chance.
Bronson Murray, who had played well when he had come on over the past two weeks, would also come off the bench.
Donnelly had looked impressive in training but a lack of game time meant he would start off the bench.
The side would travel from Johannesburg to Pretoria for the match today and would then leave for Cape Town to start preparations for the next match against the Stormers on March 12.
The Bulls have made just one change to the side which had a 25-23 win over the Cheetahs last week.
Big lock Bakkies Botha drops out with injury and is replaced by Dannie Rossouw who, with more than 100 Super caps, will team up with Victor Matfield to provide an experienced second row for the South Africans.
The Bulls have not lost at Loftus Versfeld since April 2008, a run of 18 undefeated matches.
This is their first game at home this season, and no doubt a lot of the play will centre around halfback Fourie du Preez and first five Morne Steyn.
The Bulls bolted out of the blocks last year against the Highlanders to chalk up a comfortable 50-35 win, also in Pretoria.
The Highlanders must simply play as they have been - driving into the breakdown, getting over the advantage line and not making the mistakes, although referee Stuart Dickinson is bound to have an impact on the game.
