My BJ7 tranny tunnel has no rubber gasket, and I do not recall seeing one in any of the manuals, I've left mine loose and have put a thinish layer of insulation over it (under the carpet) to help control the heat build up, it also shapes the carpet up a bit too as it is not original and was a bit baggy. When I first bought it some one had placed insulation between the tunnel and the gear box/overdrive, not a good idea from the point of view of cooling the drive train.
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