Posi, good for icy roads?
I'd go the other way, I like the limited slip diff in the snow.
I have a 2004 Chevrolet Colorado that has a 220hp inline 5 cylinder engine, 5-speed manual, and a 3.42 rearend with a G80 locker (FULL lock at under 20 mph under power), and this thing sits 3" off of the ground. This thing is a TANK in the snow. I run 120# of weight in the bed and it will go through a foot of snow like its not there on cheap snow tires. We've also had over 220 inches of snow where i live this winter and I have not gotten stuck and even pulled out a 4x4 with it. You wanna talk about trusty, this thing is it!
I just wouldn't want to drive vintage iron on the roads in the winter, that's all.