A cheap hack is to remove the center vent assembly, then reach in and force open the flap, and insert a rubber donut exhaust hanger to keep the flap open.

Later cars will have the airbag to deal with on the passenger side. Simply disconnect the battery and then make sure you don't apply 12v to the airbag connections. It is not that big a deal. I think there are some weird torx screws that secure the airbag? Don't remember for sure.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC