One thing I have done on old cars I have restored is to have the inside of the tank sealed. This, if done properly, lasts for a long time and eliminates the possibility of any rust formation. You can get kits to do this yourself but I have always had this done at one of the big radiator shops in town where they vat the tank, then seal it.

If you are worried about crud in your lines you could always disconnect you fuel line before the filter, hook up a line to it and run it to a container, then pump a couple gallons of solvent, kerosene, or something through to give it a good flushing. The Volvo CIS manual has a pretty detailed procedure for completely flushing the fuel system on that particular system.

Good luck,

Justin
83 Turbo