I'm going to call BS on the premise of the original post. Who wants to do a drive train rebuild on the bike to gain, what, 2 or 3 mph on the top end? Why not spin out the 48-14T current top gear by another 10%, or 20%? Going from 100 rpm to 120 rpm would gain you over 5mph. Learn to spin.

Or, change out your large chainring to a 50T and also spin it out. What was Merckx's top gear when he won those TdF's, a 52-14T?