Economical replacement rocker arm set?

Pull the shafts and rockers off and dissassemble the rockers from the shafts. Examine the shafts for deep wear grooves on the undersides where the rockers have been riding. It will be obvious. Wear in the rockers themselves is more of a comparative exercise between rockers; I don't know of any measurement spec to use.

You could have excess clearance in the rockers, the shafts, the pushrods, or even one of the new lifters could be not holding oil pressure due to a speck of dirt in the check valve or a faulty check valve, even being new. Even the base circle on the new cam being ground low could do this.

What you REALLY ought to do is take off the intake and measure carefully at how far the internal piston inside of each lifter is compressed below the retaining clip; this is checked on each lifter when it is one the base circle of the cam, when the cylinder for that lifter is near TDC on the compression stroke. How far the lifter piston is below the clip is 'lifter preload', and will measure typically in the .040" to .080" range for stock parts. It will show if the valvetrain parts to any particular valve has excess wear or clearance; the preload will be at or near zero for a valvetrain set that is badly worn. If the preload is low or high on all lifters, than that says there is a parts mismatch from the original geometry.

BTW, other parts can make ticks, like the fuel pump. Using a long screwdriver held close to one ear and touch various parts can help locate things like this.