What would work best is an MSD Digital 6 Plus. Do you mean TIMING retard or BOOST retard?
It has gut loads of grunt. Build in 2 stage rev limiter (100rpm adjustable) and a switch controlled timing retard (adjustable). Had mine for 2 years with stock bosch dizzy and it hasn't missed a beat.
Here's the blurb....................
Ideal For The Street Or The Strip!
The heart of the Digital-6 Plus Ignition is a 15 Megahertz microcontroller, the fastest of all digital ignitions. What this means is the controller analyzes up to 15,000,000 critical instructions per second! This is over three times the speed of comparable ignitions and produces the most accurate trigger signals, timing and rev limits possible. MSD engineers have spent an endless amount of time testing the components of the Digital-6 Plus to ensure the most efficient and reliable operation. The 6 Plus produces more power with less current draw (20% less) by incorporating an IGBT coil driver that can be controlled for improved coil saturation. Also, power MOSFET technology and high frequency magnetic converters require less input current while producing more energy and voltage. Every spark of the Digital-6 Plus ignition is packed with 135 millijoules of spark energy and up to 535 volts. When used with the MSD Blaster HVC Coil, PN 8252, a spark with over 300 milliamps burns across the plug gap for 400 microseconds. Below 3,300 rpm the Digital-6 Plus produces a series of sparks that glows in the cylinder for up to 20° of crankshaft rotation. This incredible heat ensures combustion to produce great power, quick throttle response, smooth idle and quick starts. To prevent any chance of Electro Magnetic Interference (EMI) a filter circuit is made up of state-of-the-art magnetic suppressor components. This, combined with the more than competent microcontroller, checks and rechecks inputs many times to determine “clean” signals before making any compensations. The magnetic input also features a unique microcontrolled feedback circuit for total EMI-free operation.