The problem with the Facet pumps, is that they burn out after a while, especially if your oil isn't the cleanest. I don't know why you think the stock lift pump will die without a boost pump, I never had a boost pump and never had problems with the stock pump. I think the best solution is to keep both supply and return lines, but to tee into both, then connect the two together with an additional hose. Even if you do get air in the line, all you'd have to do to get it out is to clamp off this additional line temporarily.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head