Any basic heavy vintage home machine should sew through leather just fine. For the last 30 years or so I've been sewing on a vintage Remington (post-war Japanese machine similar to Morse) that originally belonged to a friend's Grandmother. It does upholstery/leather just lovely, like a dream even -- no problems with the crotch seams from denim. I have a vintage Pfaff in a cabinet that belonged to another friend's Mom. It sews silk and fancy fabrics like a dream, and does fine with the heavy stuff too. Never could really get a quality quilt stitch out of it though, but it was fine for piecing. I'd think my 301 would do fine with leather too, but since it's not in a stand I think it might get pushed around a bit too much.
This past August a friend gifted me with her used but lovely modern machine. I've got to admit, I love the self-threader and the foot lift knee peddle and the automatic thread cutter. But I still have mad respect for my vintage beauties.