I am assuming you mean that the rockers are shaft mounted, you need adjustable length pushrods for the cam due to the reduced base circle of the cam lobe which is needed to get the increased lift in the same space. I don't care for these much because they have a tendency to break at the jam nut.
I have just one adjustable pushrod that I use to measure with or you could make one out of a new nonadjustable pushrod by drilling and tapping the ID and then fitting a stud to make it adjustable. I say new because a worn one will not sit in the pushrod cup properly and you will not get the correct length. Then I machine down the type with press in ends to get the correct length for each valve. Don't shoot for zero lash, you need some preload to compensate for wear. How much? I would say at least 0.050".
“She may not look like much, but she's got it where it counts, kid. I've made a lot of special modifications myself.”
— Han Solo