The estimate on the engine life is waaaaay off. These are very robust forgiving engines. With moderate care they will last well over 200K. Mine is a AMC 150 (4-cylinder) with well over 200K. No leaks, compression checks fine, doesn't bunr oil, and runs just fine.
Regarding the MCU (computer) they are correct. These things run much better without them. Technically, you should put in an emmissions legal upgrade (Webber carb and MSD ignition will bypass all computer control and be 49 state legal I believe).
I have an 84 too. Plan on at least the following:
new wheel bearings
new axle joints
new tie-rod ends
new ball joints
complete brake job
drain/flush all fluids
replacement of at least some seals (in engine, transmission, t-case, and axles)
possibly even a new starter/alternator/water pump
These are all parts with limited life spans and a vehicle that was most likely (partially) abused that is nearly 20 years old.