I think you will find the best option is what will work on your car for its height. I had to change mine out after I replaced the front leaf springs due to the change in the amount of travel I needed. All of the shocks listed give about the same amount of travel except the Chevy truck.
As Don listed in the other thread you have these travel ranges.
Gabriel Guardian
81676 - 11.12 collapsed, 17.73 extended
Here is what I was able to find on the Monroe
555004 GasMagnum
Technical dimensions:
Compressed length- 11.250.
Extended length- 17.875.
Travel - 6.625 inches.
Adding in a 1978 1/2 ton rear shock we get this.
Extended Length: 23.26 in.
Collapsed Length: 14.23 in.
Stroke: 9.03 in
or the front for the Cheby
Extended Length: 15.00 in.
Collapsed Length: 9.95 in.
Stroke: 5.03 in.
You get more travel length but the compressed length may be a bit long. So as said, you have to mount them and see what fits based on your expected travel in your suspension. I liked the results and think you will as well take care..