I am not sure what your looking for out of a crate engine, but most of the decent 460 crates are $5000 or more. I am rebuilding mine at the moment, and am getting it complete for about $2500. That is with performance parts, stock, you could do it for less. If you just dumping alot of oil on the pavment, replacing all the seals and gaskets is alot cheaper than a crate. I got a complete engine gasket and seal kit from Jeggs for $65.00 One thing to remember about rebuilding, you always gonna find more than you bargained for. I am running into the "Well, it is already apart, might as well replace that too." problem. It is spendy, but I am sure it is cheaper than buying a crate engine.

Good luck,
Cheers