Don't throw that Imperial away. They are nice old carbon steel although the blades are thin.
They are riveted, not pinned.
You have a few choices depending on how much you want to get into it.
You can just fix up what you have as best you can. I have a number of Imperials where the plastic has come off. They aren't Barlows and they look good enough. I have a Barlow where I've repaired the plastic covers and filled the shells the best I could with epoxy. You'll have a shell handled, possibly ugly knife. If the appearance matters a lot to you it would be a good glovebox/toolbox knife. These knives take more than you would think. I like my uglier little Imperials better than, say, a Rough Rider. They are functional and take a wicked edge.
You can take the shells off and glue some wood, or whatever scales on. I've meant to do this for a while and haven't gotten around to trying it. I'm a bit leary of the glue holding up. If it did you could make a fairly nice looking, very functional knife easily.
You can do a complete rebuild. New scales and bolsters, you would probably need new liners, and using pins instead of rivets.
Here's a link with some good links to follow in it. I think the first link is the complete rebuild. There was a great rebuild thread here on BF I was looking for if anyone can find that.
https://www.allaboutpocketknives.com/knife_forum/viewtopic.php?f=37&t=28721