Better off finding a 240sx exhaust cam and putting it on the intake side. I forget whether its the exhaust or intake cam from the altima engine you can put on the intake side of the 240sx KA, but one side has the distributor gear on it, so its a no go for that one. The other side's cam can be used on the 240sx KA intake side.
you end up with a 248, 248 setup either way you go... The 240sx setup stock for 91-94 is 242 intake, 248 exhaust. 240sx for 95-98 is 232, 232. Altima is 248 248.