My question is about valve-train equipment and when you need what.

First, guide plates. These are used to keep the valve-train perfectly aligned to avoid stress on the components, and keep the rocker right over top of the valve stem. because some of my rockers do not sit perfectly in the middle of the valve stem is this a need for guide plates. When is it neccessary?

Second, stud girdles. When are these items needed?

Well the stud Girdles are only needed on engine turning high Rpm's 7000 on up or so.

Right. Geometry is important. I would also recommend one of those inexpensive and foolproof pushrod length checkers, to ensure your pushrods are the correct length.

I have an old article written in 1955 by " Racer Brown " describing the then new 265 SB V8.They were in search of more HP and in their testing he and Frank McGurk discovered just how much the valve train would flex...They suspected something was up and they wounded several cams and also have trouble getting the engine to run past 5700 RPM....Here some of what they discovered...

They put dial indicators at the sides of several rocker arms and then rotated the engine over by hand....This showed that the rockers were deflecting as much as .008 laterally...They then placed dial indicators on several rocker studs...They again turned the engine over by hand and they discovered that the studs would wobble in all directions as much as .012 !!.Now imagine what was happening with the engine at say 5000 RPM...And this with a solid lifter cam that had a valve lift of .375 / .398 !!....Imagine what it did would do with a .700 lift roller.... Granted thats with stock pressed 3/8 in studs....but there was no way that the valve was doing what the cam was telling it to do.

Using good roller rockers and a stud girdle will tie things together into a much more stable unit.They also tend to keep the valve lash in adjustment longer...This may sound crazy but I have used Crane stud girdles in my last two engines..my 327 and my current 427...both with small solid lifter cams....I prefer to have the girdle even with the small cams and modest RPM ranges...Is it necessary to have them ? NO...But after useing them since 1988 I am convinced there is some bennifit to them...I know many people who will say the opposite and thats fine...I have no problems with that...I have run bith with and without girdles and I'll stick with useing them.