Just remember if you go big block, you'll also need a big block tranny, bigblock motor mounts, or a motor plate, Headers which aren't cheap, exhaust rewelded for the new headers, possibly new radiator for a big block.
If you were starting from scratch I'd say big block, but since you already have a small block why not get some ported edelbrock heads AND a stroker kit.
Probably do all this for alot less than the price of buying that 440 and all the stuff needed to make it run. And end up with even more horsepower than the 440 while not adding the weight!