The two smaller Allegro models carried over the A-series 1100 and 1300cc engines, but models with larger engines were subsequently added using the 1500 and 1750 E-series engine from the Austin Maxi. There was also an up-market version known as the Vanden Plas 1500. All Allegro models used transverse engines with front wheel drive. There were some interesting innovations on the Allegro, one of them being the Hydragas fluid/air suspension, to say nothing of almost universally disliked square (ish) shaped steering wheel on the earlier models.
You can see the cutaway Allegro when visiting FAST Live, which is now part of the Engineering Solutions Live exhibition, taking place at The British Motor Museum at Gaydon. The venue is adjacent to the JLR facility, less than 1 minute from the M40 south of Warwick. Almost 300 other interesting vehicles are also on display, and can be seen with a free-of-charge pass that comes with pre-registration for the exhibition. The standard adult entry price to the museum is £14.50 so act now to secure your free pass.