Standard 302s (non-HO) cams have a different firing order than 351Ws. 302HOs have same firing order as 351W. Since the firing order is different, that means the camshafts are different. You can use one in place of the other, you just have to use the proper firing order. The reason they did this (the HO&351W firing order) is that the revised firing order does not have two cylinders adjacent firing in sequence. I can't for the life of me remember if it was two cylinders that share the same crank journal or if it was same bank -- either way, it placed an undue stress on the crank and that's why they went to the other firing order for the more powerful engine.
Okay here is what little I know about this yes the 302 cam can be used in the 351W it does mean that the 302 firing order has to be used and also the other diffrence that i know of is that the 351W uses a stock rocker ratio of 1.6:1 as apposed to the 302s' 1.5:1. Not sure of the overall effect on the engines performance or any of that. my little bit of knowledge