would not recommend stock springs... im sure you could but why risk it? the 305 is a much bigger cam than stock and it will put more stress on the stock springs... an easy fix if the lt4 valve springs.. they are cheap

the valvetrain isnt something to cheap-ass your way through, a lotta bad shit can happen. even with a small cam you should upgrade as much as you can... the stock lifters will take a beating, and i havent found a good reliable upgrade, stick with a comp stock replacement or just keep your stock ones, but with springs stronger is better... same with pushrods, cmon, some nice comp 987 double springs are like 75 bucks and the hardened pushrods are maybe 100.. thats more than enough

you dont have to pull the heads to replace valve springs, use a magnet to hold your valves out of the cylinder heads, or just turn the engine to TDC at the cylinder which valve springs you are replacing so the valves dont fall in.