I know there is a version of Shoot U Full Of Love with Mark Slaughter on lead vocals. Did Mark re-record his vocals on any other Vinnie Vincent Invasion tracks? Have these songs ever surfaced?

As far as we know, any attempt at RE-recording the vocals on the debut were aborted.
There might be a few tunes . There might exist a full redo.

I believe only one tune has made it to our ears so far.

Yeah, all we have is that one song.

It's unclear how far they went with it, as I think they used it as a test for Mark to join after Rob left, along with the songs they did with Goran.

Only thing I've seen was this recording of a live concert in Canada back in 1988. Mark sings several songs from the first LP.