If you dont have a bunch of 302 bolt-ons,the 351W will be cheaper to set-up.
You would be able to use the stock crank and rods (with ARP bolts of course) or you could get some SCAT I-Beams with the pressed pins (no need to waste money on floating pins for a mild build).Have it bore/honed and balance be a good machine shop,and if you go with ARP studs or bolts for the mains,have it line bored with them.
And Grn92LX,please explain your theory further?
As I see it,the 351W will have a longer stroke,make more torque,and with a larger cam make that torque at a higher rpm.Witch will produce more power.The wieght differance isnt enough for the 347 to go by the 351W.
edit:Oh,the down side is of course the larger hiegth witch can make changing plugs a little tricker and may cause some hood clearance problems.