Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
Most modern EMUs are designed with common parts to ease construction of similar units to different specifications, and later conversions, so it would not surprise me in the slightest if they can be easily 'converted' for third rail DC operation, they are Electrostars after all, like the 375-379 units. Probably just need the third rail shoes and associated bus wires.
All the internal equipment needed is probably already in place, if it is it'd just need all the external equipment added, appropriate switches installed in the cabs and an update to the TMS