If the towers are located correctly, everything fits and the trans crossmember remains in the original location. A 351 is the same length as a 302, which had a different intermediate/adapter housing to keep the trans and t-case in the same place between 6 and 8 cylinder engines.
So in theory you're good to go.
But I can't tell just from looking if you have the mounts in the proper locations. I know there are exact measurements, so as long as you used those everything should be good.
The critical locating factor in my mind, is that it's not too far rearward. There is just no room for error between the driver's side cylinder head and the firewall. Which you can't check yet, of course, because the body is not in place yet.
Maybe someone can check some consistent areas and compare to yours. A timing cover surface to front crossmember? Rear block surface to some known point on the frame, such as the holes for the crossmember brackets?
I don't know. Maybe just compare your mounts to the measurements in the instructions and cross your fingers!;D
Good luck.
Paul