i had a reputable shop rebuild the motor and i installed it myself before i mounted it on the transmission it spun freely by hand on the crank bolt, now the issue is once the transmission is fully closed the motor will not turn if i loosen all the transmission bolts and spin the motor it spins but only when the transmission is about 1/4 of an inch separated from engine any ideas? i did have to install the flexplate could i have installed it backwards?
It sounds as though your torque converter is not fully engaged in the transmission. When installing the torque converter, you should hear (or feel) three distinct "chunks" as it goes into place. Once installed, it should be well beyond the plane of the transmission mount (recessed within the case so the flexplate has room). When you install the flexplate to torque converter bolts, you should actually be drawing the torque converter to the flexplate.
I realize you are replacing the engine here and probably didn't mess with the torque converter. The converter could have easily been pulled out of position during the operation. If the converter isn't fully engaged into the transmission, it could be causing the binding you are talking about. Pulling the engine away from the transmission should give you enough space to manipulate the torque converter to see if it will go back into the transmission any further. If you had actually gotten the engine started when like this, you would have completely destroyed the transmission.
I would think that you have an error with the flex plate, possibilities include:
One: a bolt was left loose,
Two: the wrong bolts were used and they are interfering with the casing for example.
Three: the plate is reversed (as you suggest).
Sadly for you this means either the engine or transmission or both need removing for investigation.