Need help on this one AC question

[stsalvage]

one question the center vent how necessary is it to have working cus i'm looking to put the dual speaker under the dash with Kenwood that have 180 watts per speaker and they say i can't use it do to it wont fit i just wanted to know if i just rerouted the hoses and not use the center vent will it affect how cool the truck will get i'm useing all the factory hook ups for the speaker reason why i ask i have a 1972 with only a heater and it worked in it but the round tube for the center vent gets in the way