For such a rare engine, this question comes up alot. I recently emailed someone who had a similar question. Read my response; it may trigger corrections and enlightenment from others. Maybe if we generate the proper response, I could add it to my site or we could get it added to the 700 FAQ on this site.

My response was:

"I have never compared the two blocks side by side so I cannot say that they are truly identical. I have heard that the B234F block may not be able to take a turbo add-on due to some minor flaws in the casting that is not present in the B230F. That would indicate that there are some differences. Maybe the differences come in after the block is cast (some additional mount holes drilled, etc.). But I really don't know.

The B234F has an external oil pump whereas it is internal in the B230F. I know in the old B21A that I rebuilt, the oil pump ran off a cam in the lower block that ran directly off the crank. I suspect the B230F is similar to that, hence no oil pump bolt!

The heads may be swapable in that the bolt holes may fit but that is not the issue. The top end of the two engines are very different so you would need the B230F intake manifold and exhaust plumbing, new timing gear hardware, cover plates and so on. The computers are different and likely the wiring harness is different. Not sure if any of the external items like alternator mounting brackets, etc are different. All in all, unless you have a donor car and a lot of time, it would be better to scrap the car or get a rebuild. It is amazing how one change trickles down through the whole car."

Bill
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Volvo Info Site 1990 745GLE 16valve