looked at fast, ifec, msd 

It was a fairly easy retrofit. Only a few wires to connect. They do offer a separate "Fuel Command Center" unit that handles the fuel delivery. Basically the factory fuel pump feeds the FCC and a high pressure electric pump and regulator feed the EFI unit. I went with a new tank and did the in tank fuel pump on her Olds. Just a personal preference thing. 

The key is making sure your wire connections are perfect. Especially the tach signal wire. These units rely on a good clean tach signal. There are other companies out there like MSD, Edelbrock, Holley that offer these self learning retrofit EFI units. Programming the initial setup is very easy. Just answer the questions as it prompts you and once it starts the learning process begins. I had to do a couple re-learns with my Fitech and change a couple settings to get the car to run right. It was no big deal. Very user friendly. Their tech support was decent imo.

Or you could go the difficult route and do LS engine swap route like I did.