For older carbureted cars (pre-1987), Impco carburetors can usually be retrofitted quite easily. Dual-fuel systems are a bit harder to install because a propane mixer must be mounted upstream of the gasoline carburetor and hood clearance becomes an issue. With suitable adapters and mixers slowly becoming obsolete, these types of dual fuel conversions are best done on pickup trucks and vans with plenty of hood clearance. Raso Enterprises has dual fuel conversions available for these vehicles. The challenge with dual fuel conversions is optimizing ignition timing for each fuel. For fumigation conversions, we have the AEB526N (Wolf-N) for electronic ignitions and the AEB531 (Patinos) for breaker-point ignitions.