Dave: There has been a Trad with a BMW 6-cylinder fitted into it in the past, though not produced by MMC.
However, in the case of the EvaGT the chassis according to the press release is a:
developed version of the bonded aluminium chassis of the Morgan Aero SuperSports
And as such there should be plenty of room to shoehorn the BMW straight six into it, with all the ancillary turbo gear.