Keep the frame weight low..... Before you do the actual constuction, you may want to plot out the roll center and instant center. Also get your center of gravity low as possible. Another consideration in a solid rear car is engine height and angle.... The VW front is an unknown quanity to me, but do you really want to run in the 9's (your guess), 140+ mph on a front end engineered for a 60 mph car????