Though... Yosh. Check if there's only a single BlendBySpeed or not, or if they're just the same. If it is, then you can just check if there's a BlendBySpeed and modify it straight away.
In short, like this
ForEach SkelComp.AllAnimNodes(class'UDKAnimBlendBySpeed', BlendBySpeedNode)
{
//Modify the speed threshold here;
}
Reference from https://udn.epicgames.com/Three/AnimationNodes.html