I installed EFI in my truck and kept the original tank.
I opted to use a fuel surge tank from Robbmc. The stock fuel pump supplies fuel to it and then there is a high pressure fuel pump in it to provide fuel to the EFI. I did have to run a vapor return line which was fairly easy.
I have the older version of this:
http://www.robbmcperformance.com/pro...owersurge.html
This is a video (not mine).
https://www.youtube.com/watch?v=6qmH01_fWeM