Comanche Fan, if you Find a Fix for the Rattle on Start Up, I Would Love to Hear about it, Or if I figure Mine Out, I will let You Know.
I Believe I have the exact Same issue and It's Driving me Nuts!!! 88 Comanche Renix 4.0, Runs Great, Plenty of Power, But Engine Rattles like Hell the First Few Seconds of Start Up at a high RPM or Lightly Rattling when Reaching Higher Rpm between Shifts. Mine is Definitely Rattle from within Engine, like a Dry Start