mustang 95 back half lenght shock

i have a pro street mustang 95 bbf 557 back half with 14x32 tire . what lenght of rear shock you utilize and spring rate
thank you
excuse my English french people of quebec canada

Usually a coilover drag shock with a fully extended length somewhere around the general 16" range (and a center-to-center installed ride height of around the 13.25" to 14.25" range) and using a 12" spring would probably get the job done most of the time on a generic back-half car.

But if you have a car that sits real low, and/or have enough extra room under the car (and enough shock mount adjustment), you could also try a longer body c/o shock. One with a fully extended length of around the 19" range, with a 15.5 to 16" installed height, & using a 14" spring could be used to help reduce the need to unbolt the shocks to get the slicks off a car that sits low.

IMO Rear spring rate can be a coin flip depending on how heavy the car ends up being & rear/nose weight bias. Something somewhere in the 90 to 130 lb range could be be a starting point depending on the actual race weight & weight bias.