904 to A230 worth the effort?

IIRC the A230 has a 2.95 low gear in it, but third was a bit out there. Or was it second. Yeah I think second was out there. Ima guessing something like 1.67 ratio. So it basically is like an ODbox without the od.
The od box was 3.09-1.67-1.00-.73
With the loss of the TC and it's Torque Multiplication ability, you would probably want to up your rear gear some 10% in compensation......... and there goes your fuel economy. But that's a great excuse to get the OD box instead and 3.91s, or at least 3.73s,lol.
In your wagon I would gladly opt for a longtail and put the shifter waaay further back, like between the buckets. What no buckets? That's a great excuse to get some!

Any reduction in cruise rpm,by percentage, is supposed to be equal to about half that amount in fuel useage. If that was true, then the .73od ratio would be good to drop your Rs by 27% and your HIWAY fuel economy should jump 13.5%. That would equate to about 2.5 to 3 mpgs. That might be about 80 gallons per 10,000 miles traveled. At $3.85 per gallon that would be $308. Do it in a year and your od box is paid for. Next year you can work on the clutch, the following year the shippings, and maybe by the 5th year you can start saving money.
But with 3.91s in there, forget saving money, the grin on the face in the mirror every time you shave it will be all the the payback you could ever want.