8.25 Swapping gears to Abody Unit

You say the 3.23s work well in your Duster with the 198slanty and the 3-speed.
My guess is that by 3speed, you mean the A230.
That trans should have ratios of
3.08-1.70-1.00 but could have; 2.55-1.49-1.00. Let's say it was the 3.08
the roadgears would be
9.95-5.49-3.23; So this is the standard against which to measure any improvement.
The overdrive has ratios of
3.09-1.67-1.00-.71od Roadgears with the current 3.23s would be;
9.98-5.39-3.23-2.29 , about same as with the A230, but with an extremely high 2.29 cruiser. At 82mph, your cruise rpm would be around 2340, versus 3300 with the A230
IDK if your 198 can pull 82mph at 2340 rpm.
But, I get the sense that you want to ditch the 3.23s because now you can, even tho, "they work good."
Lets say you target a cruise rpm half way between 3300 and 2340, = ~2800.. This would take 3.91s and, the new roadgears would be;
12.08-6.53-3.91-2.76, and 82=2835/65=2250
and; 35mph=2850 in Second gear, with these 3.91s; versus 2390 with the A230/3.23s.
So you have an improvement in Second gear, of 460rpm or 19%; that will put some spunk into the ol' 198. The First gear, 12.08, will take off 21% better than 9.98
So this is a winning combination in every way. Well except for with a starter gear of 12.08, from a redlight, you'll barely make it across the intersection, before the 198 is asking for a shift........... 20 mph is already 3000. but a shift into Second will get you 1620, which is a bit of a bummer, but hey, you're only going 20mph with a lightweight Duster, so, the 198 isn't exactly "lugging". 4000 will get you to 27mph, and to 2160 in Second. No matter how you look at it, this is still better than with the A230/3.23s.
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On a sidenote; I have run this combo(A833od and 3.91s) in my 68 Barracuda with a 360 engine/223 cam and it was awesome! But you know, I have also run that combo, geared at 65=1600 lol, which IMO, was the epitome of that combo to generate fabulous fuel economy.
In the end, I ditched both the trans and the 3.91s, for the Commando/3.55s, and a GVod.
Which your combo is begging for, but I understand economics. Just FYI, the Commando/GVod with 3.23s would get you Roadgears of
9.98-6.20-4.52-3.23-2.52, and 65=2040/82=2570 yummmmmmm.
35=2700 in Second, more Yummmmmmmm
and the rpm drop between First and Second is to 62% so
if you run First to 3000, the Rs drop to only 1860, not 1620.
But I know, the GVod is not cheap.
Still, selling your A230, and your A833od, and your other junk, and NOT buying 3.91s or 3.55s etcetera, will go a long way towards what I know for sure, would be your final combo.
Having said that;
Your 198 is actually begging for an AX15 ratios of
3.83-2.33-1.44-1.00-.79od, splits of .61-.62-.69-.79
This combo has been installed by a few guys who love it; and it looks like the bugs of the install have been worked out. This combo could work out well with the 3.23s, with Roadgears of
12.37-7.52-4.65-3.23-2.55; 65= 2065/82=2600 and
35=3000 in Second/1850 in Third.
Just FYI.