Shorty headers are an attempt to get equal length head pipes and end up where the stock manifolds do.
To that end they work great, but sometimes they make spark plug access almost impossible.
They will have a different resonant frequency than long tube headers.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.