this is a chevy site, not a f@rd site.
To answer your question, a "long block" is an assembled engine with a cylinder head. Or in other words, it is a "short block" with a head. This long block usually doesn't come with intake manifolds, exhaust manifolds, carbueration/fuel injection, water pump or generator/alternator.
A short block is the bottom part of the engine. It includes the pistons, bearings, seals, cam, and oilpump. The shortblock may not include any of the tins such as the oil pan.
You can get the short block and bolt all your accessories and tins to it, as well as your cylinder head, intake, exhaust and ignition. It might be a good time to have the head rebuilt, before you swap it.