to 1.7 or not to 1.7

[Cobra R...anger]

if i have an 85 5.0 H.O with lightly ported E7TE's, an edelbrock performer intake, stock 600cfm carb, 1 1/2" long tube headers exhaust without cats would i notice much of a difference in performance and what kind of a difference by using 1.7 roller rockers over using the stock rockers. also will i then have to replace the springs and pushrods and will there still be enough valve to piston clearance using the stock 4 valve relief pistons. or should i spend my money elsewhere? thanks alot for your help