I need a block for a 2003 discovery (long story, don't ask). Any suggestions? Can I use a block from a 4.0 disco and change over my parts? Where could I buy a block?

 

The blocks are the same, the stroke is different.
Check out a Rovers breakers yard...

 

Yup, blocks and heads are identical, its only the guts that are different.
You must use SAI heads on yours though, but there are 4.0's with SAI.
You can buy a totaled DII with a running engine for less money than having yours rebuilt and then swap engines over.

 

where are you? there was a nice 4.6 for $600 in the for sale section yesterday it was in MI.

 

I am located in Utah

 

Check your local Craig's list and also call Bill Davis at Great Basins Rovers in Salt Lake City, if he doesn't have one he should be able to point you towards one.
Make sure whatever you buy, you have it checked first, because there are a number of people trying to sell there junk engines. You want the vinn number of the vehicle it came from, the mileage on it and why they are selling it.

 

Still looking for a block. When I find one, what new parts do i need to have to put it together with my internals? Bearings, Rings, etc.... I have found a used short block. Would that work out good. I am trying to do this with a minimal expense. I don't think I am going to keep the car.

 

if you found a used "short block" you shouldn't need to replace any bearings, just slap your heads on it and go.

 

Here's a 4.0 that's still in running condition for $900 in Ohio. (as of March 3rd)

1999 Land Rover Discovery 4.0 Engine

 

And here's one a lot closer to you (Denver) that just happens to be a (sort of) running 4.6 from an '03.

2003 Land Rover Discovery (Parting out)