Will it work? I can only find a replacement evo 6 lower arm and not a 5.

 

I can never keep them straight but there are different control arms for 4, 5, 6, and 6.5. I dont recall the way they are and I think 1 of those pairs are common but I dont recall which ones. I think its 4 and 5 though.

 

They are both CP9A chassis. One would think they maybe the same? Try washing your question through here:
https://partsouq.com/

 

Nope, they changed the control arm and connection style a couple times from 4 thru 6.5.

 

Thanks Dallas. Heres a MLR post that notes the difference
https://www.lancerregister.com/showthread.php?t=370869

 

As mentioned in the link, the balljoint is different. I wouldn't advise it either, the Evo VI arm was mainly done to help out the gravel boys in Group N - there's a reason why the Evo 6.5 TME used the Evo V control arm again instead of the VI. It's bad for lowered geometry.

 

What RS200 says is true:
Evo 6 arms are a lot beefier Gravel spec than Evo 5/6.5TME Tarmac arms.

However, since you have Evo 6 uprights, changing anything is huge project, just get new arms- if you need to. Why?
Ball joints on Evo 6 are pressed into upright, and stud gets bolted to the Lower Control Arm Bracket.

If ball joint is bad, you can just replace it.
Even local Mitsui dealer can order it if you get Part Number.

Alternatively can get new/used arms either over internet - ebay, or even dealer. I would think they still offer new, maybe not terribly expensive.

Please explain more, asking open ended questions results in speculation, so the answers may not be appropriate, and you either do not benefit, or you have to explain it again.