Which axle Shaft for Doc Locker?

Hello all. So I'm preparing for my first transaxle locker and have decided on the "Doc Locker 2.0" for it's inherent strength in 1 piece axle and weld free (option) design, as my welding skills are still in infancy. The candidate for surgery: an MST 206-502a.

So while shopping for an axle shaft I have discovered two similar products from the same source but at different prices. One says "3/4" keyed Shaft," the other "3/4" steel live axle? Which would be the appropriate choice?

Here are the links:

https://www.bmikarts.com/34-x-36-Steel-Live-Axle_p_3646.html

https://www.bmikarts.com/34-Keyed-Shaft-_p_1045.html#

So, what's the difference and which is best suited for our use in transaxles?

Looks to be the same thing.  Same priced.  I have the Live axle one in a 206 MST right now.

@MightyRaze That's so bizarre! Thanx for responding.

Do you happen to know whats up with the MST spec numbers? For example I have MST 206-502c, and MST 206-502a. What's the difference? I can't seem to find parts for these. I can for the 206-545c, But what's the difference/are the parts interchangeable? (ie input shaft)

I wish that website gave more actually specs on materials and hardness but I would go with the one that they are selling to be used as an axle

I think the end letter on the trans number is the grade of spider gears. A is the weakest, and D is the strongest. It honestly doesn't really matter if you're gonna Doc Lock it.

But yes, I think the parts are interchangeable.

Not sure without some research. I've seen it somewhere.

@Crazy_Carl yep, some specs would be great... any thing at all. Vague description? You know the parts guy would turn inside-out if he asked what kind of machine and you said "a red one" lol

It would seem they added the steel shaft listing as an afterthought to have the "select length" option. That's just my idea though.