The other block is the motor that came out of Vivian. I know it ran well but will need new oil seals, gaskets and so on. It has no B230 stamp on the block so I'm pretty sure it is a B20 or B21.
If it's an OHC engine, it cannot be a B20. If the bore size is ~92mm, it will be a B21; if ~96mm, a B23.
If you want to keep the B230 that's already in there, it might be worth having a chat with your local blue slip inspection station, or your local RMS approved engineer. If you're friendly with your local police, it may also be worth having a chat with them and seeing who does their engine ID work in your area. In Sydney, many years ago there was a NSW Police specialist facility in Chatswood who did the forensics when the body and engine number stampings were defaced or altered by vermin car stealing scum. In most cases, they can identify the original numbers well enough to stand up in a criminal court. If you have a deadline, this is what I'd do.
If you do a re-block, you might be better off starting with an L-block from an NA 93+ 940 which will have a round-toothed timing belt, a sign that 13mm rods and oil squiters in already in there. It will be a stronger unit in every way than the existing block. NA blocks tend to have a lot less bore wear than a factory turbo block of the same mileage. The 'turbo block' is just an NA block with 2 extra holes drilled in it - one for the turbo's oil feed, the other for the drain.
530/531 heads will fit on B21/B23. Likewise, 405/398/161 heads will fit on B230 family blocks.
The B23 NA engines have the advantage of a forged crank and 'M' rods, however you'll still need to drill the holes for the oil supply and drain if you're sticking with the factory turbo oil supply hard-line pipes. Bear in mind your B23 will need a freshen-up anyway.
You've spent a lot of time and effort on new engine management and many other details so far, and done all of that in a way that you'll never have to revisit those things again.
If I wanted longevity (& I do), I'd be doing a 93+ B230 re-block. If I'd kept that 745 donor car, that's what I would've done with it - I don't have faith in the durability of skinny rod, centre thrust turbo engines. But then the 945T I now own popped up for sale at the right time for the right price, I had a deadline and tight budget to get a running wagon, the 945 needed minor things for blue slip/rego, and so the 745 project sat.
Sure - re-blocking is a major, major PITA, but IMHO once it's done right the first time, you'll never have to worry about having to go back and redoing it later, or leaving you stranded in the middle of nowhere and suffer the indignity of needing a tow home. From experience and IMHO, you're better off doing it once, as best as you can, and enjoying the results rather than spending more time under the car than in it.
