it would never stay together behind a 302 i have a c4 in my crusin wagon but nephew has a mustang 4 speed in his wagon.

C4 is a three speed automatic, no overdrive so highway speeds will be compromised unless you go with a small rear gear like a 3.25 and use big tires.  This will compromise how much power you put to the ground though. A T-5 will give you an overdrive, but will be tricky to do if you never did one.  Going back to the C4, you will need the mustang II bell housing, flywheel and torque converter to do a smooth fit.  otherwise you may have to tweek the tunnel with the BFH.