Way, way back in the day, when I was wrenching for a living, we worked on a lot of propane delivery trucks. Most of the guys that worked at the propane place had conversions on their trucks.
Lots of 460s, there may have been a FE or 2 in the bunch. Not that it really mattered what motor it was on, the systems were all the same, a metering valve that bolted onto a standard holley 4bbl flange, and a " gassifier " or boiler that's job was to turn the liquid propane into a gas before it got to the metering valve. The OP mentioned a ventury type system, Not sure if we are talking about the same delivery system.
The units I'm referring to were not great for performance because the propane ( or lpg ) in a gas form occupied a lot of the charge volume entering the motor, so it had a very negative effect on how much oxygen the motor could pull in.
It would be much, much better to inject the liquid fuel right at the valve. But back then such injectors were very expensive. Not sure what they are doing these days, with modern injectors and electronics
It might be a lot easier.
Anyway, what I remember if those motors, the oil stayed CLEAN, one guy flat out quit changing his oil, he would just top it off as needed and put a filter on once a year. The oil literally looked just like it came out of the bottle.
One drawback though, that same guy carried an entire set of pushrods behind his sea. His 460 was constantly bending pushrods, guess the propane would clean all the oil off the intake valve stems.
They also had a system that employed an O2 sensor and a small vacuum solenoid, the solenoid would dither at different rates depending on feedback from the O2 sensor, this regulated the air fuel ratio to make it "green".... though then, green was just a color, not the religious cult it is today.
