the Athearn, Kato, LBF/Hubert/Intermountain, and deLuxe cars are all Johnstown America Bethgon Aluminum Coalporters. There were three assembly variations of the car as of 2012. Don't have any information after that, but i haven't observed any major distinctions.
The big difference for the prototype is in Eastern version of the car, which were originally made of steel. the 1997 Conrail cars were stainless steel kits delivered to the Holidaysburg,PA shops to use as rebuild parts for some of CR's 14,000 remaining Carbon Steel coal cars. the cars had 11 and 12 panel sides, depending on what year they were rebuilt.
The Aluminum cars are all Bethgon II cars, and that is what was modeled by all of the manufacturers.
Overall Length Over Coupler Pulling Faces 53' 1"
Truck Centers 40' 6"
Length (inside) 47' 9 1/8"
Height (rail to top of side) 12' 8 1/2"
Cubic Capacity 4,520 Cu.Ft.
Light Weight 41,700 Lbs.
Load Limit 244,300 Lbs
Gross Rail Load 286,000 Lbs.
For your stated purposes, the prototype distance between cars should be the same.
george
N Scale Enthusiast