MKIII Brake discs - 3 sizes listed

Hi Capri fans,
 
I've been looking at Capri front discs and see that EBC list 3 different sizes for the MkIII, specifically:
 
D011 - 78-87, for 1.6 and 2.0 engine, solid 13mm disc, 27mm total height (same as Escort)
D246 - 82- 87, for 2.8i engine, vented disc 20mm, total height, often fitted to Escorts once the with caliper is spplit and spaced
D016 - 78 - 81, for 3.0 engine, solid 13mm disc but with total height of 62mm.  No. of holes is listed as 4T, although I've no idea what the T refers to.  This disc was also used on the MkI and MkII 3.0 models
 
My question is, what's the deal with the D016 and the enormous bell, i.e. why is it necessary?  Are the brakes on the 3.0 engined cars significantly different to the rest of the line up, including the 2.8i?
 
Thanks.

Before you buy them I have the vented in stock now and will have the solid here in June.
 
Will probably be substabtially cheaper than what EBC are charging

Yes