While it's not an OEM GM part, at $140 for the kit, it's cheap enough. The MegaSquirt ECU works with a distributor, needs only coolant temp, intake air and throttle position sensors. It has a MAP sensor built in, so needs a hose to the intake manifold. It'll work with either a throttle body or MPI setup. The base code for it handles only fuel, but there are a number of fuel+spark options available through alternate firmware loads. It's tunable to just about anything, from a lawnmower to a 500+ cu. in. monster. Well, maybe not something as small as a lawnmower, but pretty close. The tuning software is designed to be run on a low-end PC laptop. A number of people have installed them on AMC engines, mostly in Jeeps. There is also an active community of users involved in all aspects of its operation.
Info at <http://www.megasquirt.info>. User community is at <http://www.msefi.com>.
I know about megasquirt, but had "set it aside" thinking that I could use a stock GM ECM box and avoid the hacking. I even own a dev kit and ICE for that Motorola chip! I was hoping I could find an appropriate ECM for say a 4.3L v6, with distrib, bolt on to my 4.2L and drive. I've avoided software hackery in all my cars so far! But it's really hard to wade through all the raw info and increasingly looking like hackery is needed anyways to "tune" the GM boxes.
DISCLAIMER: One way to build a MegaSquirt ECU is through a kit that I sell.
I'd forgotten this -- found your website. You should brag about it more :-)