...finding a "Detomaso red" is a pretty good sign...! But I think I've been over every millimeter on 8ma1076, and didn't find a lick of gold (!) And even, under the headliner--no paint. What I saw was a use of a yellow primer, maybe a black sealer, and then color...The yellow was a flat, unsaturated color, very much like what I used in the 80's as an etching primer or if I remember correctly, also a BASF primer I used to like... Attached is the archeological dig on `1076--with 2 layers added in the 80's (the last an early 70's Porsche red my brother sprayed). But another place that should be telling is under the felt in the trunk, see both the yellow primer before the blackening, also traces of overspray on the shock towers. I have a very fuzzy picture also of red on the interior frame of the A pillar where then leather was added.
See also pics from 8ma1074 wheelwell and 8ma1046 (which had original paint, and if you use your imagination enough shows the black color on top of the black primer, followed by the rather dirty/grainy blacking paint that (ok, this is getting obsessive 
) heavier flat blacking paint (see the overspray on the vinyl edging trim...). 8MA1046 may have had some touchup under the front spoiler, but nothing on the rest of the car indicated the slightest touchup...
I have lots of other pictures, for example under the leather trim that goes along the interior ceiling roof--just the yellow primer and a hint of red overspray. Especially for your car, in 1976 its really unlikely that someone decided to do a color change and then hit also perform a complete disassembly, re-leathering and bare metal paint job to remove every speck on the car...And I'm sure most agree, DeT was not vigilant about hitting every spot right, there is just not a lot of attention on the car to corrosion avoidance or water drain holes (!) It seems most the car got nuked with undercoating, but paint everywhere else.
So my suggestion, paint it whatever color you want Yeah, there are already plenty of red Mangustas, but as Dick Ruzzin points out, its a great color for the car...! Lee
