The frame is plenty strong, and the small block V-8 actually weighs less than the 6-cylinder by a little bit. You'll encounter some interference problems between the steering column and the driver's side exhaust manifold. If the truck has not been converted to 12 volts, that will be necessary, as it's difficult, if not impossible to swap the V-8 starter and ignition system over to 6 volts. There should be some good info on both exhaust systems and 12 volt conversion in the tech tips section.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!