Does anybody know what the proper minimum idle rpm should be on a 4.5l engine? I figure around 1000 but does anybody know the proper factory spec?

Does anybody know what the proper minimum idle rpm should be on a 4.5l engine? I figure around 1000 but does anybody know the proper factory spec?
1000 is too high. My northstar in my Eldo idles at around 650 - 700 or so in park.

1000 is WAY too high. Do you mean the MINIMUM idle with the idle speed control completely retracted? If you do, then you're looking for 450. If you just mean proper idle, with the ISC controlling it, then you want 580-650.

In park when warmed up, my 4.9 idles around 650-680 RPM

Unless you did this already, it should be stamped on a white sticker underneath your hood, along with the vacuum settings and locations of the fpr and egr etc. hope this helps, it should be between 600 and 725 rpm.