White, if you're set on doing a SFI setup, then make sure your local LPG doesn't have a high concentration of nbutanes or other heavies which will adversely affect its vapor pressure in cold weather. If you live in one of the colder parts of Oz with freezing temps in the winter, you may have difficulty getting enough pressure in your LPG tank to satisfy the SFI system, particularly if you're building a boosted motor.
A mixer system wouldn't require as high a pressure, and they seem to be more popular in colder climates. IWEMA Enterprises make a nice system, and of course there's the ancient, but pretty reliable Impco system, and the more contemporary Technocarb mixer system from Canada.
IMHO, the best SFI LPG system out there is the Prins, which uses Keihin gaseous fuel injectors. If you check around the various LPG forums on the net, I don't think you'll find many complaints about the Prins setup, other than about its initial cost.
In terms of long term effects, valve seat recession is always a problem with gaseous fuels due to their lack of additives. If you're running a naturally aspirated motor, you might want to look into a top cylinder lubrication device like FlashLube. AFAIK, FlashLube and other similar setups won't work on boosted engines.
Here's a great place to get more acquainted with LPG technology:
http://fuelsforum.rasoenterprises.com/viewforum.php?f=5, and the owner, Frank Raso is also a dealer for the Technocarb products. IIRC, he has a video on the site showing his Technocarb system starting his Pontiac Pariesienne, on LPG, in the subfreezing temperatures around the Niagara Falls area of Canada.
