Rocker arm question

I have a stock 5.0 from an 88 mustang, I have aftermarket cobra valvecovers, can I use 1.8 rockers without any clearance problems or would I have to use 1.73, and if I can use 1.8 would I have to have the stock speed density computer dyno tuned. What kind of performace gaines can I expect from 1.73s or 1.8s.

Thanks.