Wondering if a833 overdrive fourspeed will bolt up to a 1963 170 dart with 3 on the tree
IMO; This is actually a great idea.
The factory gear ratios in the A250/A903 are;
3.18/3.22/2.95 First/1.83 Second/and of course 1.00 Third.
and in the overdrive are; 3.09-1.67-1.00-.73
But whereas 3.23s are singing
65= 2775 with 25.5" tires; the overdrive knocks that down to 65=2026.
However; notice that the Second gear goes from 1.83 to 1.67. This makes Second gear to be a long stretch from First.
The "cure" then, is to install a bigger rear-end to put Second where you need it to be, and let the rest be what it will be.
To see how that plays out, you need to convert the the transmission ratios to roadgears, by multiplying each trans-gear by the rear-gear. So here are the Roadgears with the A903 and 3.23s;
9.53--5.91-3.23; ......................and the A833od is;
9.98--
5.39-
3.23-2.36; to equalize 2nd gear, would take 3.55s, so
10.97-
5.93-
3.55-2.59; ..........However, trying to pull a 2.59 cruise gear with a 170slanty, could be a stretch. Yet to go bigger than 3.55s, means the First gear is getting to be pretty low. About the deepest rear-end you might entertain is 3.91s, thus the roadgears become;
12.08-6.53-3.91-2.85, and
65=2445 with 25.5" tires.
However; I'm thinking 3.73s would be a good compromise;
11.53-6.23-3.73-2.72/
65=2334rpm
This gives you a really good Selection of gears, except First which is a little deep. That 6.23 Second gear, compared to the current 5.91, is an improvement of just 5.4%, but 3.73 over 3.23 is an improvement of 15.5% for Third.
IMO; The 3.73s are about the best combo of A833od, and rear gear, for a slanty. Any lower a First-roadgear, is gonna put you into Second gear too early.
Happy Hot-Rodding
However, cutting the tunnel open to fit the floor-shifter, is a given; and, with bucket-seats, you get to put the shifter where you want it.