Twin spark was designed with LPG in mind as they use it a lot in Italy and Europe anyway. So the engine takes to it very well. Also the actual Twin spark helps the LPG combustion being a dry fuel.
The JTS however doesn't take to it so well. There are come kit's you can use but they tend to be pricey and they still use petrol / lpg blend rather than just lpg. Lowering the cost savings overall. Some one on here had done it but experience high exhaust temperatures. But that might have been due to the install rather than mechanical.
Basically anything with direct injection with LPG currently is in it's infancy. Where as port injection has been done for a while and the systems are very well known.
You can however put a port intake system into the JTS and have it run as long as you get the injectors as close to the cylinders as possible. But you may still get MSCF light flare up. However it will work.
If the car was an audi / merc / vw or those German brands with higher sales figures you'd probably get some of the bigger LPG manufactures create custom made systems for the cars. But as there is little sales of jts engines they are not really catered for in the same way.
Basically yes can be done. But you'll have trouble. If its the first install you've done I'd avoid it.
Alfa 166 2.0 Twinnie - LPG and a few trick performance parts