I have a 1979 Bronco that I am trying to make into an off roader.  My question is do I go with a 2.5" lift or a 4" lift?  I am new to all of this.  I know the 2.5" lift is easier, and cheaper.  With the 4" would I have to change the drive shaft angles?  My off roading will not be all that extreme due to the size of the bronco.  

the lift you want depends on how much off roading you want to do.  what type of terrain will you be going into; mostly flat with a few obstacles you wouldnt need  a whole lot of lift for clearance, or if your area is a little more technical you may need more lift for clearance and axle articulation, and that brings up another question; the tire size that you are planning on using has to be brought into consideration,  find out what other people in your area are running and see what works and what doesnt.

as for the drive shaft angles a 4" lift wouldnt make enough difference from the stock settings to require any modifications

ve always said that a 3-4" lift is best for over all performance but if you want some serious stuff then you may want to consider the type of terrian that you will be playing in. If you want rock and hills you want something that will give you a lot of flex like a full eliptical set up or 3/4 set up with a buggie spring set up or for mud well.... the higher the better