The fact that you can build up a 400 for the same price or less (cheaper/more common 400 pistons, all other parts are the same) than a 350 is probably why the 350 gets the bad rap. Same size and weight for both engines, more cubes on the 400.
If you're starting from scratch on a complete rebuild consider the readily available 400, rebuildable 400 cores can be had for fairly cheap prices.
But if your 350 is in good shape or you just want a 350 go for it, they are a fine engine.
The factory 068 cam is a good cam for a performance 350, '69 350 HO engines used that cam. I would advance the cam 4 degrees to work better with the tall 2.78 rear gears.
A good torque converter like you described is one of the best performance mods you can do on an auto trans car. I like the high quality and performance of the Continental converters, but they are pricey.
Stock exhaust manifolds won't let your 350 see 300 HP, plan on headers if you want 300+ HP. However the stock manifolds will run pretty well with a good 2-1/4" dual exhaust and will get you close to 300 HP.
A good stock rebuild with new stock springs will set your heads up just fine to work with the 068 cam. New stock replacement valves are a good idea, but not really needed if the old ones are in decent shape. The intake and carb you have are a good match for your 350 build-up.
Again, if you're starting from scratch consider the 400 engine. You'll get 30 to 50 extra horses for the same $$, not counting the price of the 400 core.
Good luck.
