How do you change the heater core in a 86 gmc sierra?

cant get the plastic cover out got all the bolts out but it wont come out so do i need to take out the dash too im thinkin i do thanks for any helpHow do you change the heater core in a 86 gmc sierra?well it depends what bolts you have taken out???. the heater box has studs that go through the fire wall that are under the hood what you are looking for they go through the fan housing i hope you don't have the one with air conditioning those are no fun but the dash can stay taking the glovebox out helps to see what your doing.