Long block is an automotive term describing an engine sub-assembly consisting of the following:

* Short block. The long block is always a superset of the corresponding short block.
* Cylinder head. A complete new or remanufactured cylinder head assembly is installed with a new head gasket and torqued to specification. Complete cylinder heads include new or reconditioned valves, valve springs, valve guides (if applicable), valve seats (if applicable), valve locks, and valve keepers. The bare head is free from cracks, warps, or holes.
* If the engine is a flathead, then the valve train is installed if the short block did not already have it.

On most engines, the camshaft will be installed. On many engines with timing gears, the camshaft will be timed.
Long block refers to a Engine pretty much minus the Tranny
and A Short block would just be the Block...

To answer your question if you alredy had a D16y8 and you going to put another d16y8 Longblock in then yes you can just use the tranny, ECU, axels, and harness to drop the new Motor in..
very easy swap
Hope that helped ya