Nice bike and welcome to BF!

I think that 7402 RD is 8-spd so you will need a DuraAce shifter to make it index correctly. You can find 8-spd DuraAce STI levers on ebay but they won't come cheap. There are also Dura Ace bar-end shifters that are supposed to be compatible with 8 or 9 speed DuraAce RD's but I've heard some folks claim they are not truly compatible, others say they are.

Anything wrong with the old fork?