If it was born in the Duster and had a 3.09 low,and 3 other gears; I expect that is the od-box, namely;
3.09-1.67-1.00-.73od Whereas..... the Commando is the same as the regular box, except for the low gear. The Regular ratios are
2.66-1.91-1.39-1.00.... Introduced in 1970 I think was a box often called the TA box with ratios of
2.47-1.77-1.34-1.00.....These are all non-hemi ratios with a 1x23spline inputs My favorite is the
3.09-1.92-1.40-1.00..... namely the Commando box. The bigger 1-2 split is worth 16% more Torque-Multiplication or nearly 2 rear gear ratios; say from 3.55s to 4.12s. The penalty is; when getting into second, the drop is also 16% greater so your engine better have some grunt down there. My 367HO doesn't complain much about it, or I just rev it a lil higher before the shift.
My stock smogger-teen didn't care either on account of it's torque-curve is pretty flat. But I can easily imagine a situation where the wide 1-2 split (62%) can be a hard pill to swallow for a smaller cid engine. However it ain't nearly as bad as the 54% 1-2 split of the 3.09od box. Every iteration I put in front of that od-box, really felt that split.
But, from my notes, if that 225/Duster had a 3-speed with an unsynchronized first, it coulda had an A903 with ratios of
2.95-1.83-1.00..... But the later Dusters woulda got a full-synchro A230 with
3.08-1.70-1.00 ....A V8 duster probably woulda had the fully synchro'ed A230 with
2.55-1.49-1.00
As you can see,numerically, the 3.08/1.70/1.00 is pretty much identical to the 3.09/1.67/1.00/.73od except of course the addition of the od gear.