the LS3 is getting to be a well known conversion for the defender here in the states.
The nice thing about an old defender is you can make it what you want, literally you can bolt on a 5 door 110 LHD puma body if you want in your garage. Rusted frame? swap it out for $3,500 in your garage... you get the idea,
Being in WA, you would also have the advantage of the tax rates a 25 year old truck brings when compared to a new vehicle (lived in WA 11 years...)
If you don't want to do the work there are a number of shops that can do it for you - a reasonable build LHD 110 is about 65k including the truck here in NC (this is the target of a current in process 110 at LRC), to whatever you want to pay for it ~$200k or more for an ECR truck.
anyway the point that i'm trying to make is it's do-able, and if your doing the work mostly, it doesn't cost as much as you may think... Its not cheap by any means but its not crazy. The Defender community is very supportive for knowledge, help, etc.
I'm hoping to get a diesel 110 in the near future.. to go with the 90