MHI-Vestas would deliver up to 42 of its V164-8MW turbine to the project 19 kilometres off England's northwest coast.
Dong has decided split the project into two phases. A Dong spokesperson said the project area had two "distinct areas" with differing features.
The spokesperson added, "This will allow us to optimise the site and create two separate phases of the project.
"This, with the flexibility afforded to us through the phased Contract For Difference (CfD) agreements, enables us to exploit the opportunity to develop the project using different technology."
A decision for the second preferred supplier has not been made and it is still awaiting a final investment decision (FID).
The Walney Extension was handed a FID-enabling Contracts for Difference subsidy by the UK government in April 2014 and was approved in November.
Last week, Windpower Monthly reported Dong Energy was looking at the V164 for the project. The developer was also the first to place a commercial order with MHI-Vestas to supply the V164 for the nearby 256MW Burbo Bank Extension.
Blades for the turbines will be manufactured at the company's recently announced Isle of Wight facility.