Length

Are Dash 9s, AC44000CWs, and AC6000CWs all the same length? I know AC6000s have larger fuel tanks and radiators, but it is harder to tell if it is longer than an AC4400. Lengths for all three, plus, maybe ES44AC would be nice!

No. The Dash 8 are the shortest, the Dash 9 are next, and the AC6000CW are the longest. I don't have the exact measurements with me at the moment.

Stuart

From "The Contemporary Diesel Spotter's Guide" (Kalmbach, 1995). First length is over pulling faces, second is separation of truck centers.
C40-8: 70'8"; 43'4" (C39-8 is same)
C40-8W: 70'9"; 43'4" (Also C41-8M
and CSX's "C44-8W")
C40-8M: 71'8"; 48'9" (These are the
"Draper Taper" carbody units
with Dofasco trucks)
C44-9W: 73'2"; 46'4"
AC44CW: 73'2"; 46'4"
--
I think the C44-9WL (or whatever it's called-- the variant with the Canadian-style safety cab-- is slightly different.)
--
The AC60 isn't covered in that 1995 book (there are more recent versions of it-- from Kalmbach and from Withers Publishing-- that do include it, but I don't have them handy), but drawings in "RailNews" for January 1999 and "Model Railroader" for September 1996 give 76' as the length over pulling faces; the former also gives a length between "truck centers" (pivot points, which are about two feet outboard from the center axle of the truck) of 53 feet, 2 and a fraction inches.
I **think** the GEVO units are at least roughly the same size as earlier Dash-9 and AC44, but am not certain. ("Model Railroader" for November 2004 has drawings of the ES44 (and also of some new and ugly EMD unit).)

Thanks, Allen! It's so easy to tell that 90MACs are longer than 70MACs, but very hard to tell that AC6000s are longer than AC44s! (Especially since the difference is only 3 feet...)

The length between truck centers is problematic. The 46'4" given for C44-9W/AC44 takes the truck center to be the center of the middle axle (this is confirmed by the C44-9W drawings in the December 1994 "Model Railroad Craftsman), so isn't comparable to the figure given for the AC60. (Since the trucks are the same and there doesn't seem to be much difference in the ends of the units, I think that-- IF we defined "truck center" the same way for both-- the AC60's truck-center length would be about as much longer than the C44's as it's over-all length is longer than the smaller unit's.)
Older truck designs had a center plate, and the truck swiveled around a pin ("center pin") projecting down from the locomtive frame into the center plate. So "truck center" had an obvious meaning. The trucks used on C44-9W and later designs -- both the "Roller Blades" design used on the C44-9 and UP/BNSF AC44 and the "Steerable" truck used on newer CP/CSX/KCS AC44 -- have a different kind of link to the carbody, with (I gather) no center pin. I assume that the two points 53'2+" apart marked on the diagram of the AC60 are the centers around which the trucks swivle.
Just one more complication to worry about in trying to interpret published data!

(((Joe-- Sorry if this is a bit peripheral to what you were interested in when you asked your initial question, but I got interested in it.)))
I finally got around to checking "The Contemporary Diesel Spotter's Guide" by Louis A. Marre & Paul K. Withers (Withers Publishing, 2000. ISBN 1-881411-25-7. On cover: "Published by Diesel Era". This is, in my opinion, a much better and more scholarly book than the Kalmbach versions, with most models illustrated by multiple (b&w) photos, and good historical commentary in the text. Marre was one of the writers of various kalmbach DSGs; apparently he and Withers decided to try to bring out a better-- though similar in eneral concept-- book in one of the periods when Kalmbach's had been allowed to go out of print. Covers most 1966 and later EMD, 1967 and later GE models, plus MLW & MK.)

Anyway, it gives 50'4" as the length between truck centers for the Dash-9/AC44: 2'10" less than the 53'2" of the AC60. Note that this is the same as the difference between the overall lengths (73'2" and 76') of the units. Which strongly suggests that the ENDS of the smaller and larger modern GE types-- pilots, footsteps, walkways, etc in as far as the trucks-- are the same, and the increased length of the AC60 is entirely between the trucks. Making them that much harder to distinguish (unless you are in a position to see the rear radiator overhang or the stepped right frame of the AC60)!

(Oh. The Canadian cap Dash 9-44CWL has the same length between truck centers as a standard Dash-9, but is 6" longer overall. Maybe "L" stands for "Long"?)