johnboyairey wrote:

I think he means keep the original block, and have it as a 4.6. That would mean fitting a 4.6 crank and con rods. Pistons will be same size, sort of.
All these 4.0 and 4.6 engines have an inherent problem, with the liners slipping down. Hence it is wise to consider the top hat type liners. They have a stepped top, and can't slip down.
If you have or get a cracked block, they seal the leaks. This problem, killed off thousands of p38 RR's as just refining,, or buying anew LR block, meant you had the same problem again. Eventually.
You either opt for top hat liners, or go for a modified block. That is not the original Land Rover item. RPI supply a better block, known as the 'Coscast' v8 block. It was developed by Cosworth. They have a lot of info (RPI) to read on their site.

If your thinking of a bit more umph, then I would talk to these chaps http://www.realsteel.co.uk/ as they mainly work on dragster engines and have built up the business around providing good service at very reasonable prices  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!