Oil coolers are good for trucks or for highly modded performance engines, but they aren't used very often on more standard SBC's. I've seen the sandwich adapters and coolers on quite a few GM light trucks in the junkyard, so you could probably pick one up very cheaply. I've also heard that the flexible lines develop leaks over time, maybe because they run so close to engine heat where they come off the sandwich adapter.
Based on your username, is this going in a Jeep? For an off-road vehicle that runs at high RPM and low road speed for a long time I think the external cooler would be worth it. However, its probably not needed on a street vehicle.