[Rev]

I think for the 289 heads you need rail rockers (with press-in studs). In high performance applications I think guide plates are preferable. The purpose of both the rail rockers and the guide plates is to keep the push rods alligned with the rest of the valve train.

In high performance applications (heads, cam, valve train) the guide plates will be what you need. BTW, a roller cam conversion may be a consideration if you're building a new engine.

Rev