B&B headers install heat backdate question

[johnnyo]

I will be installing a B&B header w/heat but only has heat outlets towards the front part Trans side of the engine, assuming I remove the rear most heating ducting and engine compartement fan assymbly will I lose the defrost heating?
What areas of the heat are covered by the rear fan assymbly also what additional sheetmetal will I need once I remove the rear heat setup, I did a search and no wherewas it indicated what eat was affected, Thanks