I have no idea what the difference between the two are...like, when youre buying a new one/or used one,, what is the difference?

(unforturnately, gf's brother had his LT1 for about 3 weeks before it go boom on the interstate)

now they are shopping for a LT1 longblock...

 

Long block is block with all internals and heads, Short block is just the block with all internals. So if your heads are still good all you usually buy is the short block.

You should tell them to upgrade to a LS1