I would follow the same pattern as all of other spec lines that have multiple listings

Chrysler Neon, (2 & 4 door) including ACR. (95-99)
Engine type - 4 Cyl SOHC or 4 Cyl DOHC.
Bore & Stroke/Displacement - 87.5 x 83.0 1995
Valves - (I) 33.0(E) 28.09 (SOHC), (I) 34.8(E) 30.59 (DOHC)
Comp Ratio - 9.8 (SOHC), 9.6 (DOHC)
Wheelbase - 104.0
Wheel Dia - 14
Gear Ratios - 3.54, 2.12, 1.36, 1.03, 0.81
Brakes - (F) 257 x 20DiscŪ 257 x 9Disc
Weight - 2450 (SOHC), 2650 (DOHC)

I don't see it as a rule change at all. What rule is it that you feel would be changed by this spec line?

Playing devils advocate, couldn't it be argued that listing them on separate spec lines goes against the rules by "creating a model that doesn't exist"? There is no such model as a Chrysler Neon SOHC or Chrysler Neon DOHC. There is a Chrysler Neon. The Neon was available in a variety of trim packages and with your choice of two different engines, a 2.0 SOHC or a 2.0 DOHC. As it turns out, the Neon with either of those engines fits into the performance parameters of the ITA class. There should be a single listing for the vehicle model, part of that listing should be any configurations that fit within the parameters of that class.