I’ll focus on the oil cross over mod alone. I’ll consider all other mods worth it if not necessary for the potential output designed within the modifications being made.
Since the original mod is to block oil and restrict it to keeping the main feed well, then the blocking of the passage is good for the intended high rpm usage it’s being done for.
Now the cross over part. Why is it done? To feed he gallery oil for the Hyd lifter of course. But why? If your going to run a Hyd cam, then is it really the cam you should be running to do the initial mod itself and then circumvent the mod?
To me it does t make sense to do a mod and then work around it to run a hyd cam when at this particular point a solid lifter cam will out power and out rpm the hyd cam.
Drilling the blocks I’ll feed to the head and maybe at best touching up (smoothing out.) the other oil gallery’s passages is all your going to need for a hyd cam. If you need to make more power, go with a solid lifter and cam. The oil coming down from the heads is enough to oil the lifters up top and the splash from down below is enough to do what’s needed.
Big hyd cams may have the goods to operate above 6500 rpm. But why when more power and rpm is available in a solid?
Let’s say that your stock un modified block is good for 6600 rpm. You need more power, the solid cam is the route! It’s just one small plug to have drilled and tapped to fit on the drivers side of the block up front. Done!
The tubing of the lifter bores & gallery should be looked at as a serious build should have this done and this is for the big solids. SFT or roller.
If you can’t make the power with a hyd cam then it’s probably the wrong cam. There also a hassle at high rpm to keep happy and set up. Heavy springs can collapse lifers, not a problem with solids, there not as stable and will not rpm like you want.
That’s what the cross over is for IMO.
IMO, it is an unnecessary modification.
Skip the cross over mod and go straight, directly to a solid cam and go!
That’s my opinion and view as well as what I do & have done & would do on future builds.