I measured the length of the rods and they are all within .5mm of each other. Although that difference is small, its enough for a gap.

 

As long as the rods are in good condition AND you set the lifter pre-load correctly, then you are good to go

RPi Engineering - Specialized Rover Engines - faqs

Turner engineering sells a shim kit. I had to shim one of the rocker shafts, but not the other

 

 

Well since you mixed up the order of the push rods, you do

 

I finished the Head Gasket job after putting the push rods back in using random order. The valve train is silent.

 

I just did that job and when the machine shop had the heads in they checked the valves. Disco has 126k miles and they said the valves were pretty much perfect. They checked them and there was no reason to lap them.
I ended up replacing my push rods because the lifters were damaged so I did cam bearings, camshaft, lifters and push rods. Two of the push rods had wear on the top but they were so cheap I got 16 new ones.