Look at this website: www.sdsefi.com

For replacing the D-Jet I would recommend the SDS. It is affordable and you don't need a laptop to tune it. I am going to do the same on a Euro 450SL with D-Jet (since no one has the right computer in the USA) I have installed the sds on many cars. It uses GM sensors and they are easy to get. The hardest part on most cars is getting the TPS set up (Throttle Position Sensor on the Throttle Body) once you get that you're home free. (sometimes it is easier to get a GM or Ford T-Body and swap it out.)

I will be supporting the MegaSquirt efi units. More info can be seen on the 190revolution.net board. I worked on the earlier versions back in 1995-6 when it was in its infancy. but these guys have come a long way. The tech help is tremendous and software is incredible.

http://www.bgsoflex.com/megasquirt.html