Outer Limits 4x4 Board

Well where to start, its a 1981 range rover 2 dr with a P76 engine and 4 speed manual gearbox. Clearly being an old engine parts are getting expensive and hard to find. After a weekend of 4wding the engine has sprung a oil leak (typical rover) and im thinking maybe of getting rod of the motor and replacing it with something reliable. Now heres the thing how much is the engine i have worth and whats the best/cheapest way forwards. Im looking at doing a few big trips so need economy and parts available.
Any advice is welcomed

Go to AULRO and post this Q as you will be flooded with advice, from fitting a 3.9 isuzu diesel to a tdi, td5 to a 6.5L v8 turbo Diesel chev , then if you want to stick with the petrol option and you have even more choice depending on the $$ YOU want to spend.
There is a company called marks 4x4 adaptors from memory who will supply a kit for several different engines to fit to a rangie. Put in a price limit and you will be led to an easier answer.
Another suggestion for a more modern drivetrain , have a look at triumph rover spares as they are wrecking heaps of landies and you could pick the $$$ level you want to go to by raiding a rolled disco, defender or rangie.

A bit extreme replacing the engine because of an oil leak, it is a 36 yo engine though so its probably time for a rebuild. Parts arent expensive as most 3.5 parts can be used bar the big end bearings and intake gasket.
I have a low k original untouched 4.4 in the shed i got for $250 so they arent worth a great deal. A 2nd hand 3.9 would be the cheapest and easiest replacement.

Well, if you had the coin, i'd suggest LS2 conversion.. hehe