Diavolo The Devil's Bike / Giant Roadie

watching your project so i'll try and answer as best i can, older aero bars tend to have a slightly smaller diameter id, i found the same with cinelli angels- if you look at retro pictures they were originally used with externally mounted aero levers. My issue was the circular bung, in my case broze coloured part was too big to slide into the bars however when removed the rest of the lever did insert- its quite laborious to shave a bit of the expander. i opted to use a slightly smaller nut that still forced apart the splines if that makes any sense? not sure if thats what your parts are like from the description as there are 2 main ways a quill is held in. Half the fun for me with these kinds of issue is engineering a solution ( some may call a bodge).Seatpost is an issue as the frame is carbon- standard removal methods may not work. You may have to sacrifice the post. Who knows if theres an alloy insert in the frame or not? 1st lube everything up. if you can tip the bike upsidedown and get any fluids to reach the other end of the seatpost internally do it- either through bottom bracket or a bottle mounting hole. * remove the saddle and the seat rail clamping parts and try to clamp the seatpost in a vice (use wood or a cloth if you want to protect the post clamp area - again bike upside down and use the bike frame as leverage to wiggle/turn. Have you tried gently tapping the seatpost upwards with a hammer, block of wood under the set back part of the seatpost and just keep lightly tapping it, the shocks may help to break the oxidisation that has occurred - dont however try knocking it further into the frame. Whats the post made of? i wouldnt heat it either way or use any corrosive method of melting it out.