For solid answers to your questions, hopefully some of those who are regular y-block engine builders will chime in on this, to include John Mummert, Ted Eaton, and Tim McMaster. Sometimes there are nuances to certain replacement component offerings that give them favor to those who have compared them to what is supplied by other manufacturers.
As a hobbyist, to me, Sealed Power is a solid name in the automotive parts supply arena. Today, Federal Mogul is the umbrella organization for ANCO (wiper blades), Champion (spark plugs), Fel-Pro (gaskets), Moog (chassis components), National (wheel oil seals and bearings), Sealed Power (engine parts), Speed Pro (performance engine parts), and Wagner (brake and lighting parts), to name MOST of their divisions.
For an overview of the history of Sealed Power going back to 1912, Google www.spx.com
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York