Hey, massaging points is an art! Both of my 429 Mercs are running single-point setups, but I've been thinking of converting one of them to duals also. By the way, while they cost a few bucks more, I've found the Accel points seem to make for more precise high-RPM firing with their heavier spring.
From what I've heard, duals are trickier to dial in but the way I see it is you can squeeze more juice out of the coil while using period-correct technology. Last time I checked, Obsolete Ford Parts (
http://www.obsoletefordparts.com) had conversion kits (plate, points, etc.) for around $40 or so. The easy way out would be to use one of those Pertronix electronic conversion kits but I'd say stick with points...