Well hello fellow hightower, I'm 6' 5" myself
As CK says, it would be very wise to get along to as many shops as you can, and try out as many different bikes as you can as well.
A road bike nowadays is a far cry from a racer of the 70's or 80's, (I'm not assuming your age here). They have different geometries and different frame materials - prepare to have your mind blown
Places like
Evans Cycles are always good to visit as they stock a lot of brands under one roof, and most people have reasonable access to one.
One problem I suspect you will experience is finding anywhere with stock of your size, (I've never managed it yet!). So from your point of view this makes sizing and fit even more crucial, but again Evans will order any bike for a refundable deposit, then if you don't want it for any reason, get your refund back and walk away.
So get along to some shops, talk to the guys, get their advice on frame size etc, (always good to compare a few for comparison), and above all enjoy the process.
I love buying a new bike I do