I went for the kit listed for the Spitfire mk I - III, Herald and Vitesse mk I from Canleys because I'm leaving my swing-axles as Triumph intended (apart from slamming it onto the tarmac).
http://www.canleyclassics.com/search...LD&ptno=KIT33B
I chose the blue 'comfort' bushes instead of the red 'sport' ones because I don't want the ride to be too hard. I've driven too many cars that've had the ride and road handling ruined by being 'uprated' for the track when they're only ever going to get used on the road.
The Peugeot 306 is a case in point: supple and well damped as standard they can be driven safely to their considerable limits. When the 'Max Power' readers start adding stiffened springs and gas shocks all they get is wheel hop, understeer and snap oversteer followed by a view of the bottom of the nearest dyke through the sunroof.
Back to the polybushes, not sure what the differences would be with the swing-spring setup, but you can buy each bush individually so mixing and matching the correct ones shouldn't be too difficult.
Good luck!