A good EFI conversion to do is www.mass-floefi.com and it's a complete system minus the fuel lines (which you can buy from them). That's my plan next time I convert anything to EFI. What I did a while ago was use the EFI setup out of a 1993 Mustang on my 67 Fastback. Massflo uses that same computer for their EFI, incidentally. As you've found out, there are two types of EFI: speed density and mass air. Mass air is easier to operate and can handle cam changes, etc. That's the main reason everyone likes using it and the speed denisty is obsolete. If you plan the Mustang route and want to use donor parts, stay away from 86-88 Mustangs. They were all speed density (I think it ended in 88??...anyway...). And for the record, 1990-1993 are the best computers. You could pick up a used 1990 LX 5.0 and have all the EFI stuff for a few grand, then part the car out and make some money back. You could even do the 5 speed swap or newer overdrive trans swap too!! But as a rule, EFI and inexpensive really don't go hand in hand for the most part. Hope that helps.