z28 question.. what should I look out for while searching?

I'm searching for a z28... i'm an import car type guy, so i'm trying to dive head first into the american muscle and get something that will force me to become knowledgeable..

first.. i'm looking at either a 2nd gen or 3rd gen model.. I know that with the 3rd gen, I would want a 5spd model..

I've also seen a 2nd gen model with a 355 and 4spd that i'm interested in..

does anybody have an insight as to the difference in power between the 2 models.. etc.. any ideas as to what I should primarily focus on engine-wise to ensure that I can eventually get some decent power out of it stock or after a few upgrades? is the 305 a legit engine? Should I go out of my way to get a 350 or will a 305 do the trick?

in the 2nd gen i've seen.. is the 355 going to be the LT1?
I'm kinda lost.. I do VG30DE's.. not american muscle..
Thanks