Your best bet is to check out a third gen site... like http://www.thirdgen.org/
- they should have some tech articles, and some knowledgeable people on this subject.
As far as 305 vs 350...you can always make a 305 perform...but the more cubes you've got, the more power you can make, and still be more "user friendly". You gain about 15-20% more performance from a 350. And, if you're starting from the ground up rebuilding it - the cost difference is about $150-200 ($100 for a 350 block core, and $50-100 for a crank core). And then everything from there is similar. Or, if you don't want to go the fully balanced, align-honed, decked, indexed (i.e., partially blue-printed) route, but just want a solid engine to start with for solid, but not radical, performance (say 350-400 hp or so), you could pick up a GM replacement engine for about $1350, (or a short block, better yet), and add some decent heads, 1 5/8 headers and 2 1/2 inch dual exhaust, a decent cam (220-230 degrees at .050), and modify you're intake for sufficient fuel supply, and you're there.
383's (a .030 over 350 with a stroker kit - 3.75 inch stroke instead of 3.48), and 406's (.030 over 400) are also options - more torque, more cubes - same basic block (the 400 block is a little different, and has a couple issues, but most parts - heads, headers, cams, intake, accessories - will bolt right up, and they mount the same). I don't know what your head choices are limited to with the TPI - the third gen site can help you. Or, you can do a bunch of reading and learn about all your options...the smartest route.
The first questions are, how much power do you want to make?, and how much money/time/expertise do you have to spend?
This is a fairly good site for general, and fairly specific, small block chevy, and big block chevy, as well as, obviously, 1st gen camaro advise. And for everything from mild street performance to fairly wild racing performance. But for issues specific to the third gens, you're better off looking there for advice. Though there are a few people here with knowledge on the subject, educating kids with little automotive knowledge and with 3rd gen questions tends not to be high on the priority list of many of the people here - and that's what MOST of the 3rd gen questions posted here get to be.