For the ultimate in driveability, economy and user control your want sequential port injection (which requires a cam signal), on a single plane manifold with a self learning ECU controlling the timing. For a system like this you should consider the FAST XFI system. I would not suggest the EZ retro kit (that's the one that for port injection), because it's bank-to-bank only and it does not control the timing.

The FAST XFI is more expensive than the MS and a fully built-up MS system can do the same thing as the XFI. Here are my comments:

1) The GM ECU would work fine as long as you can get a hold of good tuning software. I like the HpTuners for serious manipulation of GM ECUs. The ECUs are wide band compatible, they do not auto tune, they do not data log, and the tuning software can be expensive. However the hardware is "junkyard cheap" so this is probably the least expensive way to go.

2) The MS-III can do everything you need, but you sort of have to "join the club". If making harnesses, reading schematics, and if you are fairly technical in electronics, it's a great way to go. It's an open system which means it doesn't really have a feature list. You more or less decide what you want and build it from there, but you can buy a complete ECU already assembled. The MS-III can do sequential injection, use a wideband, control ignition and data log.

3) FAST XFI. This system can control anything you want, it does self learn, is very well known and well supported. Heck, Summit sells the parts and FAST offers an off-the-shelf dual-sync distributor for your motor. But it is the most expensive too. A typical FAST XFI system will run about $1500 more than the MS-III. The other ECUs in this range are the Accel DFI, and Big Stuff -3.

From your post it looks like you are up to any of these solutions so good luck and lets see some pics of whatever you decide to do.