I tried to log in this morning when you posted, I have done 135,000 in my 4.0 ltr P38 without any problems, mine is a Zavoli sequential system fitted by A.B Garage, Hawarden Chester. It has had only 2 services on the gas system only to change the filters and to check the system was fine during normal servicing. I get 200 to 220 miles to a full tank (tordial in the wheel well). It refills with 60-65 ltrs of Lpg each time.
I say go for it, just get a good P38 to start. Hope this helps.