Just came across something that showed the setup on the Escort S1 and RS1600i. Apparently these have tie bars/compression struts and a separate arb as standard. The tie bar/compression strut goes through the tca, as the arb would do normally. And the arb is clamped to the compression strut.

I suppose this should also work on the Sierra setup, although you would need to be able to fit both the arb and compression strut to the arb mount on the chassis rail. But I've seen some brackets from Turbo Technics to do this.