Most SBC don't use torque specs for rocker arm nuts. You will have valve lash or just adjust to the point where the rocker arm stops making noise as is cycles. Thing to do is look at a manual for your year engine, then check how to set valves. My friend just sets them to contact the valve stem at the right setting on the crankshaft (both valves fully closed for the cylinder in question), then backs them off a tiny bit when cold. He warms the engine up, loosens them one at a time until they tick, then tightens them to where they just stop. But a look at the book for your engine would be best.

Unless you're using an aftermarket cam, in which case, you'll want to check the valve lash the cam maker calls for.

Hope this helps.