For older vehicles (1987 & older) with V8 engines, Impco recommends their Model 425 system for carbureted engines up to 460 CID to a maximum of around 4065 RPM for that displacement. This is strictly based on the air flow capacity of the mixer which is rated at 460 CFM @ 1.5” Hg and a volumetric efficiency of 85%. If you have a big block engine in your pickup truck and operate it at mainly low engine speeds (below 3500 RPM), a single mixer dual fuel system would work fine. If you want high performance from that truck, you might want to consider a dual Model 425 carb intake but this is very unconventional for propane engines.
Besides the Model 425 mixer, you might also want to consider replacing the standard gas valve with the lean (PN AV1-1644-2) gas valve for better fuel economy. You can to add an electronic feedback control unit to your engine for emission control. However, the Impco feedback system gas valve (PN AV1-1651-2) is designed for feedback operation but there is a possibility that the standard gas valve may provide better fuel economy. To make the system work, you need to plumb the mixer into the induction system and both Impco and Gann Products Company still have adapters for common applications. See our Model 425 Mono-Fuel Conversion page for more information.
Modern fuel injected vehicles are not commonly converted to straight propane but instead are usually converted to dual fuel. Technocarb makes injection kits to fit a wide variety of modern gasoline and diesel vehicles. Because the best and safest way to convert a vehicle is through a licensed propane conversion centre, you will need to discuss your application with one of their distributors who will then install a kit tailored to your needs. Technocarb’s products fit a wide variety of engine sizes and are typically sold as complete underhood kits. Check our conversion shop page for local listings or search for automotive fuel conversion or propane conversion systems on Canada411 and on SuperPages.
If you are mechanically inclined, you could probably do this work yourself but, at least in Ontario, the regulations require a licensed propane mechanic to perform the conversion. If you are comfortable with the work outlined in the Dual Curve manual on a DIY basis, you might be able to find a local mechanic who would inspect your work and possibly put the finishing touches on it. This is something you will have to find out for yourself.