Ok, The ancient Huret Allvit on my 1974 Raleigh Record is fading finally. I just got a mountain bike derailleur off a Huffy Mountain Bike.
I know, please don't LOL too hard. But it did have Shimano SIS components, so I stripped it. Those old thumb shifters were pretty cool in their day, some still swear by them.
I figure any type of Shimano is better than that Huret.
The Huffy MTB had a five speed rear cog, so I think this will work. Has anyone ever tried this? I noticed when you go on REI's site they don't list MTB or road, just whatever speed it is. Hmmm. And God, are derailleurs expensive new. whew.