[MrPbody]

cbell,
I'm real curious. Please post here when you've run it on a dyno or at the track. For track info to be meaningful, I need to know the weight of the car, and what tires you use (rear, size and type).
Just for information purposes, a C-4 is a "Cruis-O-Matic". That was Ford's name for all the automatic transmissions of the day except the "Econo-Glide" 2-speed. That is, a C-6 and an FMX are also "Cruis-O-Matic" transmissions. Ther are a couple of variations on C-4. The "heavy duty" version is also known as C-5, among transmission men. Not to be confused with the later "C-5" found in Fox bodies. You can tell the early C-5 at a glance by the bolts holding the bellhousing on the case. If they don't go through the pump body, it's a C-5 (there will be 2 complete sets of bolts around the pump). If there's only one set, it's a C-4.
It should be a reasonably good performer. In olden times, 289s and automatics were recipe for a lead sled. Today, with converters at affordable prices, things have changed. Look for it to run around the 14.0 mark (1/4 mile). You MIGHT squeeze it into the 13s. A good set of slicks and some traction equipment would go a long way in your launch. Don't be disappointed if it doesn't go "12s" first time out.
Above all, if you like the car and are having fun with it, it doesn't matter how fast it goes. "Fun" is the operative word here...

FWIW, my brother is real into Mustangs. If there's something you need or something odd you know where is, let me know. He might be able to help, OR he might just want it...! He has a show-stopper '65 "K-Code" (high performance factory package). Nice looker but it won't touch his '99 Cobra.

Jim