The pair are part of the eight strong New Zealand team - six are from Otago - preparing for the International Paralympic Committee world championships in Qatar later this month.
With the temperature reaching 36degC in Darwin, O'Neill set a 200m record with a time of 31.4sec at the meet.
He also holds the Otago 100m record (15.61sec).
McSweeney was also in good form in the javelin, beating his old record by 2.37m with a 52.79m throw in the F44 class.
The temperature was not as hot at the Caledonian Ground on Saturday as in Darwin, but there was some exciting action in the third track and field meet of the season.
The race of the day was in the women's 18 19 years 200m, in which Hilary Harper, of Christchurch, pipped Taieri's Christina Ashton on the line by just 0.02sec.
Harper finished in 26.49sec to get the win, but the finish was too close to judge with the naked eye.
It was a similar story in the 100m, as Harper again got the better of Ashton at the finish.
The Christchurch runner stopped the clock in 12.56sec, just 0.12sec faster than Ashton in another thriller.
There was also a good race in the men's 15 17 years 800m, with Matthew Ogle (Hill City-University) beating out Taieri's Sam Gouverneur and Leith's Nathan Hill.
Ogle finished strongly to win in 2min 5.98sec, while Gouverneur was not far behind in 2min 8.98sec.
Hill was third in 2min 9.15sec.
Among other highlights on the day
• Terry Collins Hawkins (Hill City-University) clocked the fastest 100m (11.06sec) and 200m (22.38sec) times of the day in the men's 20-34 section.
• Rory O'Neill (Ariki) clocked good early season times in the 100m (11.34sec) and 200m (23.04sec).
• Felix McDonald (Taieri) won the men's 15 17 years 100m in 11.56sec.
• Emma Ward (Taieri) had a good win in the women's 15 17 years 100m (12.89sec).
• Joccoaa Palmer (Taieri) won the women's 15 17 years triple jump (10.61sec).
• Caitlyn George (Hill City-University) won the women's 15 17 years 100m in 12.84sec.
