I've got the 'goodwrench' engine like the one you posted in my suburban. It gets the job done, but isn't a powerhouse. The HP rating they list on those is if its has headers and performance intake, carb, dist, ets - so if you bolt on old stock stuff you won't see that.
I added an edelbrock EPS intake, Summit 1102 cam, MSD ignition on mine and it woke it up a bit, but not much. Biggest thing that holds those engines back is the low compression heads. A vortec head crate engine would be a nice upgrade, but you'd need a different intake.
Here is an article where they build one up.
http://www.superchevy.com/how-to/463...e-engine-build