Be careful you dont get too far ahead of yourself ..

Personally ... I wouldnt be worrying about engine replacement until after making sure the leak is not the things - mostly mentioned in previous posts ...


Water pump gasket,
Water pump weephole,
T'stat Housing gasket,
T'stat housing cracked,
Heater hose extension pipe on waterpump rusted out,
A split in a rad hose,
A split in the rad plastic end caps,
A split in the rad core.

That eth-gly is slippery muck ... and compared to water alone - will find the smallest gap to seep out of.