[jpnovak]

I would rebuild the original engine and keep it with the car. The market's do strange things and you don't want to separate unless you have to.

I would do a full rebuild at this mileage unless you have documentation that the bottom end was done. At this age the intermediate layshaft bearings will be all copper as well as the thrust bearing. Best to get in there and inspect and replace. Most likely you will find more wear on the rod bearings than mains.