Sorry, but that is not correct. The Montreal was never planned with a mid-mounted engine. The prototype was designed on a Giulia Sprint GT floorpan from the start (and that's where the lack of time comes in) and initially got a 1600 from a Giulia TI.
Carlo Chiti and other Alfa engineers denies in Luigi Giuliani's book "Montreal" that the car was planned with a mid engine and that the persistent rumours about that fact is due to contemporary sensationalist journalists. The slats were nothing more than a stylistic detail to visually break up the large areas of sheet metal behind the doors. Marcello Gandini (the designer) denies it too in the same book.
A mid-engined Montreal would have made it prohibitively expensive, something Alfa didn't want. They were, after all, out to fill the gap after the 2600 and to make amends for the botched 33 Stradale project.
The 105.33 project in turn, was (marketing-wise) a move Alfa did in order to compete with Fiat/Ferrari and the Dino-engined cars. They wanted a V8 in their lineup, and they finally got in in form of the Montreal.
So, no mid-engined Montreal was ever planned by Alfa Romeo.
Tutto Basta!