As far as I have concluded, the first 700 series car was the 1983 V-6 760 and it had remained V-6 powered until Volvo decided to end its use with the 1989 model year. The 740 entered in 1984 and was always a 4 cylinder only model if gasoline powered, as the 6 cylinder diesel was available in both models until '86 or '87.

In 1988, the B200/230 engine got 2 major changes to improve reliability due to the original friction reducing specifications that made it weaker than the B21/23 that it replaced. The main bearings were enlarged to 63mm from 55mm, and the connecting rods enlarged to 13mm beam from 9mm. It was not until this design engine, sometimes called the "K" block, was introduced that the turbo version returned to the 760 model. I know that 1989 had both but the turbo engine MAY have also been available during all or part of 1988 model year. Another change was made to this engine in late 1988 and affected some early 1989 cars - the thrust bearing was relocated to the rearmost location from #3 to strengthen the crank further. The late 1988 - 1995 B200/B230FT is erroneously called the K block - the designation belongs only to the short production with large journals and thrust bearing located at the centre postion.

Another change incorporated since the first 1988 change is the inclusion of bosses for the piston cooling oil jets that did not actually appear in production until June 1992 (for 1993 MY cars).

While the 760 got both versions of the large main journal crankshaft, the 780 Bertone (built off the 760 sedan) did not receive turbo engine until 1989 production after the thrust bearing was relocated.

The V-6 was no longer available in either model for 1990. Sedan vs wagon did not affect engine choices...with the possible exception of the 1984 B23FT.