Here's what I would do to avoid spending more cash than necessary:

What t-case did the V4A51 have behind it? If it is a round six-bolt pattern on the front of the t-case, then you're probably good to go.

If not, buy the AW4 tailhousing. Remove your tailhousing and see if it fits. If it does (pretty sure it will), just keep your transmission and swap a 231 onto it. <img src="/forums/images/graemlins/kewl.gif" alt="" />

If it that doesn't fit, then think about swapping transmissions and you will have the tailhousing you will need anyways.

If you're serious about a swap like this, then dropping a t-case to verify stuff is no sweat. <img src="/forums/images/graemlins/mrt.gif" alt="" />