Altering dimensions of a block in design center?

Hello, 

I am currently designing office layouts in AutoCAD, and I am using the blocks provided in the design center.  The block I have inserted is a desk, and the dimensions are 30x60 inches.  I would like to change the dimensions to 35.5x71.5 inches.  Is there a way to change the size of the block other than scaling.  I have had success in scaling up to 71.5 inches, but that does not give me my desired 35.5 inches of depth.  

Thanks!

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