I recently picked up a 1972 413 from a motorhome for free and am in the process of rebuilding it using the tall heads and the big waterpump. Ive been able to get a hold of every part except the center row head bolts. Theyre the same bolts as a normal big block mopar but there about an inch longer. I also couldnt find exhaust valve seals, because the exhaust valve diameter is bigger than normal because its sodium filled. Any help will be appreciated.