Jeff, I had wrote mid March/70, it’ actually March 12/70 build date....
Missed that
at that time of night. And the mentioned reason I didn't think it was the time to do an in-depth response at the moment
.........I’m not doing the work myself, but trying to provide good info for the job.
Yes this seems to be the typical practice we often see today in many examples. The owner doing the research for shops not able (time or effort) to do it themselves.
So looking at March 70 at Dearborn I don't have any examples of red oxide use originally form covering the front frame nor the main floor section. Its great that you do have examples of the original colors still visible in your car. So many erase these and only realize too late that we can not provide exactly what you car was painted with only what other cars around your car came with.
There appears from reports and pictures, that there were small periods when red oxide was used likely due to a supply or mechanical issue with the normal batch paint process or plumbing. As mentioned in the earlier threads the matching or using the same source for both firewall forward and the main floor may be the results of replumbing of the supply lines for the paint guns and sprayers at both stations rather than the earlier separate sources.
Also as a results of the brighter colors available in 70 and allot of fine overspray the visible final look of the main floors (away from the heavy spray of body color out towards the pinch welds) and the hidden area in the drive line tunnel can look very different from the base and the combination of the two can produce some interesting colors and in turn result in three basic colors. One from the body color, one from the base first coat and the combination of both
Bottom line it appears you off to a good start we invite follow up and new questions so that you can get the foundation of the car that fits your pan. Everything after this step is bolt on and much easier to correct or fix while choices here can drive or eliminate possibilities in the future
Good luck with you choices