Hmmm, have you thought about re-tapping/re-threading the bolt holes? If it's a good running 250, I don't see anything advantagious about putting a 230 in. A 292 yeah, I'd do the swap.
As far as differences, don't think there's much aside from the obvious. I was buying parts for a 230 for quite some time and then found out I had a 292! If you're already set on doing a swap, I'd try to find a 292 and make it worth your while.
