[Dru]

To check your vacuum advance, look for the cone shaped metal piece on the side of your distributor, with the small hose coming off of it, its showing in your bottom picture, couple ways to check it is, while the engine is idling, pull the hose, and listen for any change in rpm, or you can pull your distributor cap, and either use a vacuum pump on the hose, mouth..or whatever you choose, and see if its advancing the timing, there is a ring in the lower part of the distributor that the advance mechanism rotates.

Your carb is good, there would have been a electrical plug going into the top of it. It looks like your distributor is good too.

Im not sure of your transmission type, but one other thing you might check, is if it has the electrical lockup turbo 350 transmission in it, it looks like everything else has been switched over, but if you could crawl under it and check if your transmission has a wired plug going to it, the lockup torque converter might not be working anymore. There should either be a plug, or a socket around top of the sealing edge of the transmission pan.

Sounds like you picked the best fan, since the other had no clutch.

I dont happen to have any info on quadrajet tuning, its something I've never got into myself, the metering rods, and pulling the top of the carb off to change it all, just a pain in the butt, and they were replaced with Holleys.

Unless you install a air/fuel ration gauge, you'll have to install a fresh set of plugs, put a few miles on them, and then pull them for a read on the color.

I honestly don't know much about running LPG either.

Hope you get your mileage up, 6 mpg seems pretty bad to me, I'm hoping for better mileage out of my big block once its all wrapped up.

Edit: I just noticed Geezer gave a few good methods to check the advance too.