Thanks to all for the responses, greatly appreciated!
I have an LSD jaguar rear end, ( that did not sound right) the car is listed as a GRX from the original sales title, as well as the GRX complete manual that came with the car.
I will get the 75-90 and add the posi additive.
The tranny will get the 80-90 GL4 treatment as soon as I get the oil delivered this week.
Once a few checks are complete I will take it for a ride and post a few more pictures.
Someone asked what I paid for it, my reply was is a little less than I thought I was going to have to pay. Not sure what the range is for a pretty nice car, but maybe some of you would have an idea.
What information on this car is:
Charles Hillard Ford, Fort Worth Tx. bought the car in 09/11/81 ( used the car in the sales room for photo shoots with customers, painted it black at that time form the original yellow. ( there is a little yellow in the engine bay and it is a color I would not have picked ).
Russ Janeake purchased in 10/01/90 with 5814 actual mileage
T. Brooks purchased in 3/02/82 6451 actual mileage
F. Wendelken purchased ( Colorado) 7/11/98 11,965 actual mileage
Then Rich Bieling ( CO). 14,362 actual mileage, Last time it was registered from F. Wendelken was in 2008. the car just sat at 8000k feet above sea level at his house in Colorado. ( occasionally fired up but not driven, as the roads were not good).