
Guest, it sounds to me as if you need a heck of a lot more knowledge before you go about this whim. there are hundreds of lurchers from such whims, residing in rescue centres desperately in need of homes :(
To give a brief answer to your question, a lurcher is a x between a sight hound and a pastoral breed. eg greyhound x collie. A long dog is mix of pure sight hounds ie whippet x greyhound. the exception to the rule in lurchers is where bedlingtons are added to the mix. certain people are also infusing bull terrier blood
:( but personally I do not approve of this, being a lurcher/longdog purist myself.
Before you start on some irresponsible, ill thought out breeding idea, you need to have a proven working hound, which is put with the utmost care to another suitable dog, with the knowledge of the sort of puppy you are wanting to produce e.g a rabbiting lurcher for sandy soil or a hare coursing longdog for stubble, or a foxing lurcher for moorland or????? the list goes on but you need to know all this first.