There is enough space under the hood for an RB. You may loose the inner fenders, and probably the fresh air for the heat, neither of which you probably would have left intact anyway.

The front suspension, if its in good shape will support the RB's weight. It is a decent suspension that parts are available for at many auto parts stores and online. Improvements can be had by moving the shock from the upper control arm to a bracket on the frame, kits are available to do this, but its pretty simple. You definitely want a disc brake conversion, several kits are offered. Its cheaper to do a disc brake conversion then it is to rebuild the original brakes, which would be inadequate for a RB powered car.

The rear suspension, if in good condition will support an RB, but I would swap out the usually open rear axle for something a little bigger, with a sure grip, and much more modern,. The original brakes and rear drum setup is poor design, and the axle flanges are keyed to the axles and probably wouldn't hold up to an RB with traction, which the open diff probably couldn't supply anyway.

You want to make sure the car your looking at has a good frame. They tend to rust out in the lower part of the front cross member, and on the frame rails in front of and behind the leaf spring mounting points. If the frame is not rusted beyond repair and is not bent, they are plenty tough enough for an RB.

It will be required for you to post up pictures and keep us informed about your build. Gene