Here are my corner weights on my 77 280 set up for BSP with driver and aprox.8 gals of fuel.   
  
Lt. Fr. 705  Rt Fr 724  
Lt. R. 753   Rt. R 697.   
  
That is with a stock 6 and 5speed with coil over susp.  And now with a zz4 crate,t56 6speed, weir bellhousing,front and rear bumpers removed,battery relocated to rt rear, with the same coil overs set at exactly the same ht. as before.  The only other major diff is know it has tub. cntrl arms.  With driver and 10 gals of fuel.   
  
lt. fr. 706  Rt. fr. 695   
lt.R.765    Rt.R.729.   
  
The car gained 18+/-lbs 355hp and 405ft.lb.  The car still has complete interior with all the stock glass and a roll bar that is scca solo 1 legal.  You decide if a V8 upsets the balance of a Z. 
  
[Edited by Drax240z: for clarity]