Just finished rebuild of 727. installed. haven't add fluid yet. won't go into reverse or park. Any suggestions.

"Haven't add fluid yet." If there is no atf in the trans, how do you expect it to work?
If it doesn't go into park or reverse (with low fluid, I wouldn't expect to get reverse, but not getting the shifter to reach to reverse is a different matter), it sounds like the shift linkage is messed up. What year is your J10, and are the body to frame mounts good? Bad mounts will cause problems with shift linkage. Gene

thanks poorboy. I wanted to check if the gear selector was operating normally before i added fluid in case i had to take the pan off for any reason before i added fluid.
linkage was messed up. Thanks for the advice. Im new to the jeep mopar world. looking forward to this project. Thanks again

With the linkage disconnected from the lever on the trans, you should be able to move the lever on the trans the full distance. Park is at the end of the lever movement (can't remember if its forward or rearward end), and should lock the driveshaft from turning. From there you should be able to feel each gear detent in the lever as you move the lever by hand, park, reverse, neutral, drive, 2nd, and low. If you can feel each detent in the trans, put the trans lever back in park, put the shift lever in park, and adjust the linkage so it will connect to the trans lever without moving the lever. Gene

That is exactly what i did to set my mind at ease that i wasnt going to have to take the pan off. thanks again. i really appreciate it.