CNG, not LPG, currently costs about half the price of gasoline in the Los Angeles market. You loose about twenty percent on power. The problem is that the high pressure parts are very expensive. CNG is dispensed at 3200-3600psi. If your truck is EFI, you MAY be able to find a junked Crown Victoria CNG police car or taxi and get the necessary parts, then reprogram the system. Even so, as was posted above, a 460 is still way too thirsty.

Jim