Like most everything, the answer is "it depends". LOL. If the crack goes all the way to the center and there are any cracks around the center web/main area, then I'd not risk it.
I'd love to try laser welding, but I don't know enough about it.
However, if you can identify the ends of the crack and drill them, then potentially aluminum-bronze braze it with TIG on AC, might be worth a try. I only have a DC TIG, so I'm sort of stuck with silicon-bronze rod.
Some guys don't pre-heat the block, that doesn't make a lot of sense to me. I'd make a nice BBQ pit, get a bunch of coals nice and hot and put this sucker in there! I'd also have some thermal blankets to put around it when I pull it out and after welding - to cool it as slow as possible. Another option is a big steel drum full of vermiculite.
The other real question is how much time/effort are you willing to put into it? I doubt I'd do a full-race type build - due to the number of hours of porting, relieving, valve work, special MAINs, etc.. I wouldn't invest that much into it . . . at least today! LOL