should I modify my joints and create a slip joint in my 87 FRONT drive shaft? Or buy a ready made drive shaft? get a rear drive shaft and convert it to a front? need some wisdom here...
Go to yotatech and see some good examples. Some people have even made their own out of square stock. You'll only use the front d/s for slow speeds so balancing the d/s isn't really necessary.
Your front drv shft should already have a slip joint. However, depending on the final result of your SAS (amount of lift and travel) you may need a long travel slip joint, in addition to a longer drv shft. You could have your stock shaft modified, a complete new shaft built to your specs, or make your own. Your call.