tufcj
Not sure on the mounts. Jeepsr4ever will have to answer that.
The 304 will bolt in, but you may have to re-drill the flexplate if it's an automatic. AMC V-8s are externally balanced, so you need to keep the 304 flexplate of flywheel. You may also have to have a custom pilot bushing made to adapt the crank to the trans. The I-6 is internally balanced, so you can't swap the flywheels.
Bob
tufcj