If your cylinder compression is ok and you're not blowing any coolant hoses, you may only have a very small leak (most likely a head gasket). If the engine is running fine otherwise, why do the swap? The only advantage I can think of is that you'll be able to drive your VX while your doing tests and rebuilding the replacement engine. Otherwise it may be less expensive to do a top rebuild (new gaskets, etc).

The 99-01 VXes all had the same engine - although supposedly the later models had some slight modification to get more oil into #1 cylinder. The complete assemblies should swap right out though.

-- John