It could be more helpful if you said what type of problem you were having.

A new overflow valve from Fast Lane was around $28 + shipping.

to do the test for the Over Flow Valve; and for sure on the Fuel Supply/Lift Pump you need a liquid dampened Gauge or as one of the members did he made some sort of damper.

Personally I do not see how stretching a Spring will in the long run help. If a spring has collapsed some it is because it fatigued. You can stretch it but I would expect it to eventually return to the collapsed state.

__________________
84 300D, 82 Volvo 244Gl Diesel