I built several rods from that article, using the 601(5 foot), 720 (6 foot) and 721(6 foot) blanks along with the 781(6'6").
Should be able to do a 5/6/7wt off the 661-2 (5'6" 2 piece) I found the 601 cast a 6 weight rather well.

Best thing is oversize the guides by one size, then you can use it as a dula purpose spin/fly rod or just a spinning rod.