I made custom dual shock brackets for my 71 C10 4x4 and since the mounting point was different I had to pick a different set of shocks which were operational within my new length. If I were you I would measure top to bottom mounting point then check out different shocks on
www.summitracing.com. Most of the shocks I looked at gave a minimum and maximum length. I went with shocks which were close to the middle of the range installed and had room to compress and extend as needed.