An idea triggered by apophenia's comment
here. This will be a little convoluted but bear with me.
During WWII, Australia developed its own tank called the Sentinel. One of the odd things of this design was that it actually had 3 engines forced upon it by the unavailability of preferred options: three Cadillac V8 engines – petrol car engines with a displacement of 346 cu in (5.7 L) each installed in a clover-leaf configuration (two engines side-by-side to the front and a single to the rear) with all feeding power to a common gearbox:
Now back to the Mirage. What if during some scenario (be that a WW3 style event or possibly even something equivalent to COVID but in the late '60s/early '70s), Australia finds itself building new fighters but suffering from lack of the preferred 'bigger' engine. They do have access to smaller ones though. Long story short, the Mirage III airframe is mated to 3 Armstrong Siddeley Viper turbojets instead of the single SNECMA Atar 09C.
Looking at comparison:
| SNECMA Atar 09C | | Viper (as used in MB-326H) | | 'Triple Viper' |
Thrust | 41.97 kN (9,440 lbf) thrust dry, 60.8 kN (13,700 lbf) with afterburner | | 15.2 kN (3,410 lbf) thrust | | 45.6 kN (10,230 lbf) thrust - not sure about with afterburner performance but let's maybe say 58.8 kN (13,230 lbf) based upon the version used in the IAR-93 |
Dry Weight | 1,456 kg (3,210 lb) | | 249 kg (549 lb) | | 747 kg (1647 lb) - without afterburner but lets say the afterburner adds another 250kg taking it all up to 997 kg (2198 lb) |
Diameter | 1,000 mm (39 in) | | 624mm (24.55 in) | | 1270mm (50 in) - based upon cloverleaf arrangement |
Note that I left out length as I doubt that will be an issue. Theoretically it would be doable though you might end up with a fat bellied bird a bit like the Mirage III T: