what exactly is different???

what exactly is different from a 1984 5.0 302 carb'ed engine and a 351w when it comes to try to use pistons,headers,cam,crank from the 302 engine to get it work in the 351w? I was told the intake manifold and headers were really different.

well i would assume the 351 has a bigger bore and stroke, hence the 49 extra cubes.

The 351w block is taller, hence the extra cubes. So, if you installed 302 headers on a 351w, they would hit right into the fire wall/bulk head. Cams are the same, cranks have a diefferent stroke, but they could fit, etc. 351w intake is a little over an 1" wider.