If you do go for the Cobra 1.7 roller rockers while you have the stock heads and later decide to upgrade to aftermarket aluminium heads, you won't be able to reuse those rockers unless you choose pedestal mount heads (most are stud mount). Your choice of camshaft will also be restricted to one that has less than 0.500" of valve lift with 1.6 ratio rockers so that you don't run into piston-to-valve clearance problems.
If aluminium heads are definitely in your plans, I'd follow Grady's advice and get stud mount heads with 1.6 ratio stud mount roller rockers. The stud mount heads already have pushrod guideplates and rocker studs, while the main advantage of the stud mount rockers is their adjustability, thus making it easy to set the lifter preload without needing to buy pedestal shims or different length pushrods. The TFS and Holley top end kits already include fully assembled heads, stud mount roller rockers, hardened pushrods, and taller valve covers so you don't need to piece everything together.