I dont mind sacrificing some economy for reliability, which i feel i would be getting from an older japanese petrol- but would LPG be potentially unreliable!?
If it’s installed professionally by a reliable fitter then it shouldn’t be unreliable.
I would say that the only thing you need to be careful of is LPG drying the engine out – regular oil changes are a good idea (like every 5 – 6000 miles) and run it solely on good quality unleaded every now and again – something like Optimax or V-Power.
Bear in mind that unless you are doing regular long trips you probably won’t see any economic benefits at all – LPG systems start up on petrol and take a couple of miles to switch over fully onto gas once they are warmed up.
I ran a Volvo S70 on a single-point ssytem for about 3 years with no problems. I don’t subscribe to the reduced performance argument, it felt no different in response/torque over running it on neat petrol. I do agree that consumption figures will be down over petrol by about 10 – 15%.
Tank-wise, a donut tank in the spare wheel well will allow you to keep full load space at the expense of being able to carry a spare wheel, so you may need to budget in for run-flat tyres too unless you want to carry a can of tyre-jizz and a compressor, or rely on the breakdown services.