None of my reference pages had engine code 43, but if you follow the Volvo numbering scheme of those days, a code 43 would be a B21 engine, most likely a B21D engine. Hadn't heard of that variant so I fired up a search engine (or two or three) to see if it ever existed.

I found one mention of it on an '82 260 apparently listed for sale in Germany or some such. So we know the 260 had that motor available probably somewhere in Europe. The VIN includes the Volvo plant and market codes so you should be able to figure that out.

I found a fairly detailed Volvo engine list (slow) on Dmitri Bladov's personal website (Russia). Although there is no specific mention, using the generic B18/B20/B21/B23 designations it seems that a B21D would be a variant of the standard B21A carburated engine, but with higher compression and twin carbs (possibly SU or Zenith-Stromberg). Makes sense to have such an engine on an upscale 260 -perhaps for a market where a bigger displacement engine like the B27 or B28 would have been taxed higher.