with the 242 how do you get by with the full time front axle turning the xfer yoke?

I have a 231 on a 5 speed. I am told depending on shaft length it would work same as the 242.

I found a 249J in a local JY for 600$. I would need to further test mine before rolling the dice on another used one.

I see on ebay they have a new viscous coupling unit for 400-600 so a used complete working case should be a fair deal.

what else is needed to bolt in a 242 case?

how hard to rebuild a 249 case replacing the coupling?