Without a picture of where the split is it is difficult to come up with a repair plan.

With the Line off of the Car it might be possible with a Flux Core type welder to weld over the bad area. Or, Heliarc welding would also work.
Both processes heat a smaller area and would be less likely to heat up the Rubber Hose enough to damage it.

Also I do not see why both hoses would need to be replace if the other one is not leaking.

Looping the Hoses together is safer than Blocking off the ports.
There is a thread several weeks ago on the but concerning 617.95* Engines. Some felt blocking the Oil Cooler Ports would cause the Bypass Valve to open and dirty Oil would be circulated through the Engine when the Oil Filter Thermostat opened to divert Oil to Oil Cooler Ports.
I felt that the Manual said the Engine would still get clean oil but neither thoughts have been proven.
And in your case you have a different Engine and the Oil Filtration system may work differently.
So it is safest (or at least gives the closest to normal Oil Flow) to loop the Hoses together.

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84 300D, 82 Volvo 244Gl Diesel