To get the power out of a 302 on propane you will have to increase the compression ratio and run a RV cam. I have had 2 trucks on propane I hated it they burned more fuel than they did on regular gas. One truck it was 460 on propane the sucker would suck down 30-40 dollars worth of propane like nothing. When I converted the truck back to gas it had alot more power and it got better fuel mileage.

The main reason why I converted back is the system on my truck needed re-inspected the tank needed replacing plus other parts needed replacing. I priced it out it was cheaper for me to buy a brandnew gas tank,remanufactured carburator and fuel pump than it was trying to get the propane system legal again.

The DOT here and the rest of Canada has clamped down on propane systems they really tightened the rules. The reason why is the Taxi cab companies in Vancouver B.C. running Taxis with improper and very dangerous set up propane systems running their cabs. It was pretty leinient before but now everything has to be absolutely perfect if there is something wrong your vehical is pulled off the road.

One of the shops here used to install and service automotive propane systems when propane power was common as propane was 30 cents a litre compared to gas in that day was 60 cents a litre then some parts of Vancouver you could find propane for 10 cents a litre. When you had a big old 454 or 460 Ford it was worth it to run propane if you could get it for 10 cents a litre.

I haven't checked what the price of automotive propane is per litre lately its been 10 years since I had a propane powered truck.