Alrighty, so I did end up getting some OEM springs, but they honestly made no difference. I guess these don't really wear out over time. I ended up picking up a set of assorted springs from Home Depot (pictured) for around $5 and they came with a size that worked perfect for this application. Didn't bother measuring them, but they fit inside the OEM spring decently snug and are pretty much the same length. The coils are a little thicker than the OEM spring coils and take a bit more effort to compress. They have really taken out a lot of the slop from the shifter. So much so that I don't think I'll need a short shifter anymore.
