The problem with the head is going to be all the little bits you're going to have to machine or buy. I'm pretty sure the little lift arms will have to be modified and I know you will have to make the rods that connect them. I even had to make a few parts when I went from a D2 to a D5 and I had all of the hardware from the D2. A whole D5XL with a color head and power supply ready to go can be had for two or three hundred dollars.
I can't stress this enough. Right now darkroom hardware is cheap, take advantage of it. Spend your time making photographs and your money on nice materials. If I hadn't gotten the D5 chassis free (and I have a mini cnc mill and a 9" lathe) I wouldn't have bothered.
Enjoy your printing. Your conversation has convinced me to do some myself this evening.<g>