1970 duster heater box

I bought this heater vent hose kit for my 1970 duster, which came with no instructions! It seems to me, that after I put the two rubber spacers on the vent tube necks, there appears to be, not enough room now, to install the hose's and clamp's. I was wondering if any one else has ran in to this same problem and how they corrected it? Did I buy the wrong kit or just installing it together wrong?

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