I work on a chemical plant, on which we store great amounts of explosive chemicals. There is a greater potential for LPG to cause more damage if it goes boom, but the control measures put on the systems and the quality of the tanks manufacture reduces the chance of this happening. Petrol/LPG risks are similar burning fireballs. Diesel, still burning fireballs but lot harder to ignite. We have pyrophoric chemicals which ignite when they see air too which is great, which was the old leaded fuel additive.
I drive around in a V8 with LPG system fitted, I am not worried about the system, valves have to be energised to open as previous posts, fail safe closed etc.
I have also had big 4x4 diesels in the past, to go anywhere fast in a diesel (one I had) dropped fuel economy to 17 mpg, didn't matter too much at the time becasue I was making Biodiesel for about 40ppl, when my chip fat supplier started selling me the fat I gave up and mothballed my little plant.
I am so glad I got a petrol this time. Its an absolute pleasure to drive. I haven't driven the diesel P38 so don't know what it goes like, but the engine is very well made, I bet a little more reliable than the 4.6 v8. But the V8 is an Iconic engine which was put in so many cars trucks over the years loved by many, theres a reason it lasted. Its is excellent.
Added.
Sorry, forgot to mention, I live quite near an LPG filling station that is reliable. Without that I doubt I would be doing as many miles in the RR as I do.