Assuming the 740 is similar to the 240 and I think they were very similar, the fuel sender unit should be mounted on top the fuel tank. It is integral with the fuel pump. You may have a cover plate you can remove from the floor to reach the top of the fuel tank without removing the tank. This ...

FCP page for '92 740 NA "fuel sending unit" -
https://www.fcpeuro.com/Volvo-parts/Fuel-Level-Sending-Unit/

<EDIT> They're not showing a pic here, but you could hunt around using these part numbers and see if it matches yours.
https://www.fcpeuro.com/products/volvo-fuel-tank-sending-unit-740 ...

See if any of these are any help -

http://www.voluparts.com

This site lets you drill down to your exact car and then system. There are parts diagrams to help you see what it all looks like -
https://www.volvopartswebstore.com/cars/Volvo/1992/740-5DRS-SR-23l-Fuel-Injected/Engine/740-5DRS-SR-23l ...

92 wagon 740 non turbo.

Im fairly certain it has the "regina" system not that I know what that is. Google is of little help defining what rex regina is and the same with locating this part.

Thanks for any help.