It's too bad the RamLine stock set was discontinued, they can be made to look pretty nice with just a little work. MPI makes fiberglass stocks for Marlin levers but they're pretty pricey.
http://www.mpistocks.com/availablestocks.htm
Check with Wild West Guns also, they may have synthetic stocks for your 336. Keep an eye on ebay and maybe post a WTB over on some of the other lever gun forums.
I put a RamLine set on my old 336 years ago, in a panic I discovered the forend on my rifle was cracked just a few days before a hunt and RamLine was my only real option to make the gun serviceable in time. I thought it would be a temporary fix but I was really happy after I got them installed. It was a tight fit to install, I had to remove just the smallest amount in the tang area. Now a few yrs later it seems like the plastic has relaxed a bit and the fit is about as perfect as it gets. I don't know the exact weight difference, but they're noticeably lighter then the original wood stocks.
Since then I've painted them with rustOleum Multicolor textured spray and put some grip tape panels on the forend. The paint has proven pretty durable, I've only resprayed once in the lase 5 years. The other thing was the buttstock had a cheap hollow feel and sound, I pulled off the buttplate and filled the stock with GreatStuff foam. Now it has a nice quiet solid feel. If I were building another 336 I would definitely try to find another set.