Make sure the engine is worth the work
I have to agree with the idea of the other posters to take the engine out and really look into it to have a total picture of the condition. I've had too many experiences where I repaired something in thr bottom end- or top end for that matter and then had to go back and address another failure. When an enigne fails mechanically it's usually a sign of another problem or the end of a gneral wear cycle. I had a Leyland A-series engine that knocked only for a few days and when I pulled off the sump there were pieces of a big end bearing lying in the pan. With an 1/8" gap between rod end, the crackshaft was battered beyond usability. I did have one success though and I replaced rings, rebuilt the head and big ends in a Volvo 122S with the engine in the car and supsension dropped down, but that was an engine with 90,000 miles that didn't need reboring and the crankshaft was in spec.
Good luck on that one!