Ditto what BKM said. For a sand rail the only doner pcs from the bug are the front and rear suspension. All of those can be had thru aftermarket and depending how serious you get with suspension the bug stuff is very limiting anyway.
Where you are there should be plenty of built rails for sale for cheap, start with something used and then build it to what you want.
http://www.thesamba.com/vw/
http://acmecarco.com
http://fisherbuggies.com
Mine was an old bugpac frame, really low windshield hoop and pretty short wheelbase.
My Rides
1985 250R original (Garage Queen)
-under restoration
1985 250R black and blue full rebuild ( Daily Rider)
-Paul Turner pipe
-+2" Westcoast
1985 Red and White Tecat-EH Sold
1985 Green Tecate Sold
My Wife's Ride
-2003 Suzuki LTZ 400 Showroom fresh and completely stock
My Kids Ride
-2004 Yamaha Blaster, Completely Stock
-2006 Yamaha Blaster, Completely Stock