I just bought H&R super sport springs for my 97 cobra (31K miles). Do you think I have to replace the shocks and struts . If I do should i put in the Bilstein . I mostly do town driving . Thanks for the advise guys.
#1 If you can afford it yes, like the others said you'll have it taken apart anyway and it'll be much easier to do all that at once.
#2 When I installed my springs on my 98 with only 30k miles I ran the stock shocks/struts for about 4 weeks. Well when i replaced them with Tokico's I could compress them by hand and they didn't even spring back. The stock shocks/struts are designed for stock ride height. Prolonged use with lowering springs causes them to wear because they are always at a more compressed rate (due to the lowering). It will greatly help ride quality if you get new ones also. Billstein are great if you have the cash.