Hiya Phil and welcome to the forum.
FYI. I have a 2008 Granturismo (left) which I'll be advertising in a month or so. Just waiting to get the MoT done.
Its a public system here in N.I. so when the unions mess about, the wait time goes nuts.
Anyhoo.
I also have a Range Rover Classic with an LPG adaption, so I might be able to offer some observations.
Many insurance companies are a bit luke warm regarding LPG. Some won't insure LPG adapted cars.
Those insurance companies who will insure an LPG adapted car, usually demand an annual inspection and certification of road worthiness by an accredited LPG installation engineer. This gets more problematic as LPG engineers become fewer. Any old accreditation won't do. It has to be the British Association of blah de blah.
Can't recall off hand what they're called. Some also ask for a copy of the system installation certification and again, it must be by an engineer with the right accreditation.
I'd imagine that an LPG adaption might lower the value of the car. In the eyes of purists anyway.
In my area, I've seen the number of petrol stations with LPG pumps shrink from half a dozen to one, in
a few years. If they're not doing enough volume to warrant the expense, you'll arrive one day to find the pump gone.
It's a little bit messy (or at least my system is) when filling the tank. But there are no extra smells etc once the tank is filled. LPG systems can work in SUVs because you can have a choice of what shape of tanks to put in different places.
So-called torpedo tanks are popular. Fitted one per side to the chassis. You loose a little range, compared to a big tank in the boot, but since the point of an SUV is it's load carrying capacity, why would you destroy that by having a big tank in the boot?
So far as I understand, you don't really have a choice with a Maserati. Its the boot or nothing. Is this something you can live with?
On the economics of LPG. It all depends on the size of your tank and the relative prices of LPG and petrol and whether you fill up on unleaded or super unleaded. From memory, you also get less mpg from LPG.
There's not really much point, me commenting on the RR Classic, since your numbers will be different.
I think, I brought my mpg up from high single figures, with the standard Rover 3.9 engine, with a chilled driving style. To high teens and exceptionally, low twenties. So, it does make a difference. But, ONLY if you have a competitive local market and high demand for LPG and you're fitting it to an SUV.
You'd want to research how the LPG market is trending. Last time I looked, around three years ago. It was definitely in long term decline and with every manufacturer backing EVs, I'd suggest that this will only increase over time.
If we were talking SUVs, I'd suggest a diesel. A Maserati with LPG sounds as odd as a flying chicken