Hivot5.0.. you should be ok with the higher pressure cap (13-16psi) with your modern 302.. but I have heard of people overheating there old flat heads when using a higher pressure cap (stock is 3-4psi).

I would think that a new Radiator could be able to take the higher 13-16PSI pressure without problem, but I am not sure if the water pump and block/head is designed of a old Flathead would be able keep that amount of pressure without blowing something out ??? what do you guys think..? (I could be wrong, and it wouldn't be the last time...LOL).