4-5 speed gear linkage

Hi,
I want to change my standard 4 speed box to a 5 speed one and wanted to know if i need to take all the 5 speed linkages from under the donor car ( as this will be tricky at a scrap yard) or can i just connect the old linkages to the new box and screw on the 5 speed gear knob to the old gear stick? What i am woried about if i use the 4 speed linkages is that there wont be enougth room in the dust cover to get it into fifth gear.
Any help appreciated.......mcd
 
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