the A15 was a forklift motor too, so there are complete lpg sytems that bolt on. not sure they're suited to driving a car since the industrial A15 was rated at like 42HP.

Propane seems to run 'lean' if you want any power out of it. also propane likes higher compression that most A series motors have.

I actually have too much carburettor, it's about 60mm with a GA16 throttle body,it needed a restrictor put in the intake to get it more vacuum signal.

using omvl equipment, seemed more suited to cars than impco.

i've struggled with fuel economy ... 18l 100km is about 15 mpg, thats' about as good as i've ever gotten in the city.i've had 30 mpg+ on the highway. i look at it as lpg is 1/2 the cost of petrol, so i'm getting 30 petrol mpg even at the worst ... 20 petrol mpg city and as good as 60 petrol mpg highway.... creative accounting? not any more than a hybrid...

the short answer is a turbo... lpg likes 12.5:1 compression, economy should be much better then, if you can keep your foot out of it. debating just buying the turbo already and getting started...