The adapter can be found cheaper than that.
Nothing wrong with a hybrid swap, although they can get interesting finding parts.
Yeah BBC this and that, what would be the total cost of acquiring one then rebuilding it with installing it? If the Olds motor was gotten cheaply enough, much of that cost will be saved during the rebuild phase as opposed to just 'aquiring' a BBC.
Olds and Pontiac motors have a lower torque curve due to their larger strokes. This makes them very good candidates for truck motors.
If you plan on revving that motor, then attention needs to be paid to the oiling system. For low rpm grunt work, then this is not an issue.
Investigate the heads a bit. Once again, with both the Olds and Poncho, the power and compression ratio will vary a lot with just the head.
Changing spark plugs on that Olds will be a breaze.
Good luck with your decision....