The problem with converting a .410 to 32 ga is primarily primer spacing. The 32 ga ammo is made in Europe primarily for old single shot "Garden Guns". The Fiocchi ammo is 1/2 oz of soft lead atop a brush wad. I think half the load is roughened up judging from the lead left in the barrel.
and.. Fiocchi hulls are not made with reloading in mind. One maybe 2 reloads and the hulls are done. and.. you have to roll crimp. I made a 32 roll crimper from a 28 by soldering in the brass ring from a spent Fiocchi hull. The ring is brass coated steel and can be made to fit.
Ballastic offers a 32 wad with petals. It's too long to fit in the Fiocchi hulls. My 32 was proofed at 70mm in 2003. I have yet to find 2 3/4" 32s in America.
I think of the 32 as a 50 cal shotgun. It's actually a bit bigger, .516? My notes are not nearby. Converting a .410 to greater than 50 cal, that's a lot metal and the primers wouildn't line up.
Better to search for a 32 ga gun.
RST was making 32 ga ammo. It is way better than Fiocchi. I don't know about availability in today's market.
I'll have my 32 at the Southern SxS. Track me down.