Here's my thoughts on it.
If money is an issue, then I'd go with the DSII, however for $50 bucks I would purchase a rebuilt unit. A used dizzy may have a lot of miles on it, and a worn bushing can cause top end timing fluctuations. Next, I would use the Dyna module (and coil), as it has more dwell than the GM module (see comments below). Flash_point did a nice job installing and wiring his DSII with the Dyna module. It looks great.
http://classicinlines.com/images/Tech_i ... I/DS13.JPG
Complete article
http://classicinlines.com/DSII_swap2.asp
If money isn't an issue, then I'd go with the DUI. At first, it looks out of place because it's so much bigger than the stock or DSII dizzy. But once it's in there for a while, it looks right at home. Nowdays, when I look at a stock dizzy, or the DSII, they look out of place.
The DUI is very easy to wire up and very clean, and it looks like a performance distributor when compared to the other two. Plus it's billet, instead of cast, and has a full length bushing. Service parts are cheap and readily available.
I wouldn't even consider the Petronics, unless I was trying to keep a pure stock appearance.
Bottom line, it's all a matter of preferance, and cost. Either one is a huge improvement over the stock dizzy. We are currently trying to set up an account with the company that rebuilds and supplies the DSII dizzy, so we can offer them at a better price, along with the Dyna modules.
What is a Dyna Module, and why is it better?
A few forum members have stated that a stock GM HEI will perform just as well as the DUI, and that a DSII wired to a multi-spark ignition box (such as the MSD) will perform better. This is incorrect. Multi-spark ignition systems utilize an external capacitive discharge, while the DUI incorporates a high dwell Dyna module, which increases the coil saturation time. As a result the DUI coil produces a single long duration spark, as compared to multiple sparks, which has been proven to improve throttle response and low end power. The longer saturation time, along with the 50,000 volt coil, also allow the plug gaps to be opened up to .055". Whereas stock GM HEI ignitons, and many multi-spark boxes, recommend a gap no larger than .045". On top of this the DUI coil and module only draw 2-3 amps, rather than the 6-10 amps, which results in reduced coil temperatures. Therefore the DUI not only makes more power than the GM HEI, or a multi-spark ignition system, it's more reliable.
When purchasing replacement parts for the DUI, you can use stock GM HEI parts such as the module, coil, cap and rotor, which can be found at any local auto parts store. While the stock GM module will get you running in case of a breakdown, it will not provide the same performance as the Dyna module.
