Can a mangekyou sharingan user awake Eternel Mangekyou, by only transplanting a pair of Normal Sharingans, or does it need a pair of MS?
No, they cannot. It is in the manga and in the wikia. 


  ...usage of the Mangekyō Sharingan's abilities can cause a great strain on the user...it can cause considerable damage to their being, leaving the body in agonising pain and causing deterioration to their vision until eventually over-usage leaves them blind. Their vision can be restored by transplanting the Mangekyō Sharingan of an Uchiha with strong blood ties — ideally a sibling — thus awakening the so-called Eternal Mangekyō Sharingan


As far as I know, there have been no cases where Eternal Mangekyo Sharingan awakened simply by transplanting 'normal' Sharingan eyes unto a Mangekyo Sharingan user.