I wouldn't draw the line so clearly. Seems to me the "320 european" isn't really one cartridge, but a whole family of cartridges. I've had several revolvers in that rough 32 caliber range and some were as small as .310 and one was .327 . Also the rim thickness and diameter, as well as case size varied a lot. the .327 gun had a really thick case mouth recess cut in the cylinder... so the case size was far larger than you would expect. My safety measure is to check if a dummy 32 SC, 32 S&W or any other no-go caliber will fit before buying.
So, in short, I can't offer any advice on loads etc, but I can correct the assumption that .320 european is the same as the prohib 32 cals... instead it's more a catch all name for the one hundred and one different calibers made by bicycle shops and small time gunsmiths across europe that fell in the .30 to .33 caliber range.