I agree the cracks will only get worse and you should not ride them, not that I have not put a few miles on my own wheels after seeing a crack, not not a strangers wheels NEVER

as noted if the price is lowenough it is a good starting point to get a pair of campi hubs and learn to build your own. the nice thing about these older tubulars is usually the ERD is close enough that if the spokes are in good shape (again not certain I would do this for a strange wheel I just bought) you could simply tape the new rims to the old and cross the spoke over.

there was a thread with some nice looking Campi tubular rims NOS for about $50 a pair out of Germany some where, OH 36h