If your 350 is stock, the toy gear will hold up well. If you are quick to smash the skinny pedal, it will end up letting you down. The gearing in your diffs will need to be dropped WAY down, or you will wear the engine out. 350's are happiest around 2000 to 2500 rpm, so gear down to where your hwy/cruising speed is in that range, and you'll be good. The added rotating mass of the engine will be your enemy if you lift a tire and drop it back down under high rev's. (axles and birf's) The added weight of the engine will also drop the front suspension 1 - 1 1/2 inches, and will bottom the springs out quicker. You will need to increase the front spring rate to compensate for this (add an extra leaf or two - long leaves). The exhaust manifolds or headers will make a tight fit between the frame rails, but will fit. You may want to consider getting the SHORT water pump, and moving the drivetrain forward, for the distributor to clear the firewall, or grab the BFH and clearance the firewall. A 4-core radiator will probably be needed to take care of heat, and I would reccommend a electric pusher fan for it. I see you are already running a carb, so you know the carb issues, but would reccommend at least the basic TBI setup for it. You will also have to consider the oil pan/axle interference.
With the proper setup, the added power makes it a very attractive swap. 350's are pretty durable, just don't overheat them. Parts are plentiful and available everywhere, and they are pretty easy to work on. I have considered the same swap, and have done a lot of research on it. If you go that route, definitely keep a build thread! Hope some of this helps!
