Boy howdy that crossmember is waaaaay too low. You'd hook on a speed bump and would never get it on or off of a trailer.
I see that you have the rear end sitting on jack stands. That means the rear suspension as it is set up NOW is in full compression. If the driveline was installed it would clear the crossmember as you have it mocked up in the pics, BUT the crossmember is too low. If you were to lower the rear suspension, you could install a straight crossmember instead of the dipped one as shown. Another way is to use a round tube crossmember which will give a tad more ground clearance.
Step one is to set the car up on jackstands and make a reference diagram for your actual desired ride height. That also includes exactly where the rear axle will be and may require disconnecting the shocks and making setup bars to go in place of the shocks, or using 3/4" allthread in place of the shocks to compress the rear springs to your desired ride height. Install the trans without the engine, then install the driveshaft. Now you can see where and how much room you have to work with. Don't forget to leave enough clearance for the driveshaft when the rear suspension is completely unloaded.