Considering a rear leaf spring replacement, new KYB Gas-a-just shocks and adding a rear sway bar.

Current springs are 4 leaf. Classic Industries has 4-leaf and 5 leaf and in the description, it states that 4 leaf were used on high performance application but I have read elsewhere that 5 leaf were more heavy-duty (Tamerz). Classic charges $50 more for the 4 leaf ($200 vs. $150).
I am looking for stiffer spring rate and perhaps less bottoming-out when backing out at the end of the driveway or pulling into an incline.