If you can soulder, Megasquirt PCB3 ECU Fuel Injection Injector EFI Kits | eBay
Get a harness to go with it, a junkyard throttle body, temp sensor, air temp tensor, and o2 sensor plug (new o2 sensor) and you have a very good EFI system that is quite capable- down the road upgrade your intake to a multiport EFI system for even better results.
BTW these can also easily control spark timing with a stock chevy distributor from a TBI or newer vehicle.
Your total will be around $400 if you don't mind going to a junk yard.
Here's a preassembled unit, though its not as nice, its a MS1 v2.2, still more than adequate but not as many bells and whistles as the PCB 3.0, megasquirt v2.2
I'd offer him $150 shipped.
Here's a preassembled MS2 unit, which is also a little better than both of th eprevious but a little more costly- Megasquirt II 2 PCB3 Standalone Engine Management ECU | eBay
BTW, these units are both upgradable to control COP ignition and sequential EFI if you really feel you need every last bell and whistle. All of them do nitrous control, dual fuel tables, boost control, fan control, etc in even their most basic form.
In the end it really makes you question buying a $650 carb...