i have a 351w block 40 over in my garage wityh the crank rods and pistons. do you guys think it will be noticable step up from the 302 if i put a good set of heads pistons cam and intake on it?
To fully take advantage of the increased displacement you will need a good h/c/i combo. Stock heads are no where near adequate for a 351w. There are tons of threads on this swap here, so the search function will actually be useful for this topic (most the time it isn't that great).
With appropriate heads cam and intake the 351w will be a major improvement over the 302. Also the 351w block is considerably stronger than the 302, so the potential for big power in a stock block is better.