Injector line pressures are too high to contain in rubber hose. That's why they're metal to begin with. I suppose not having backpressure from the injector will mean much reduced pressures for the rubber hose. Still could get messy at higher rpms.

You can use the #4 line from any 60x engine if there are wrecking yards near you.

The usual cause of injector line failures is inadequate clamping. Make sure the line clamps and spacers are in place and functioning. Overtightening can stress the flare and cause the line to come apart right at the fitting.

Sixto
87 300D