Whitey,
I have a G grade Lefever here and took a quick look at it, it doesn't have any underlugs or bites. The only thing that keeps it from opening at firing is a rather hefty Dollshead extension with a locking notch cut into it across the back of it. You might just get by with it for a 32-40 but as stated previously, it will make up into a very heavy 32-40 at best. If you have to use it for conversion, I would humbly suggest making it up as a rifled shotgun. We know it will stand those pressures and it won't be as heavy when finished. You might also consider sleeving it back to a smoothbore. How long are the remianing barrels? If you have enough length left, you might consider putting chokes back in it.

I'm not sure how well the damascus barrels would thread for the use of screw-in choke tubes, but there are solder-in, fixed choke sleeves that could be added. Bob