904 in the wagon took a dump, any help to be had?

In my opinion, a later 904 with the lower gearset, also known as the A-999.... This is the easiest way to go. All the 80s Fifth Avenue cars had them. 2.74 1st gear compared to 2.45 for a standard 904. These had lockup converters and were all hydraulic. Simple.
Next up would be the A-500, essentially a 999 with overdrive. You'd want an early one though since the functions to control the overdrive is able to be done with a toggle switch. I am not sure if the 500 converter clutch is still hydraulic or electrically engaged.