Replacing FAST EFI on HP 383, with what?

I got the duster 383 back from the first shop. Put in a MSD Billet with new plug wires and wiring. Changed all the fluids, plugs, filters, etc. We wanted to see what we would get with the 383 getting good spark and timing more precise so that we could really find out how the FAST efi was going to perform. It sat up and laid down like a dog. Started great, idled great, sounded super. Took it home and called it a "sack-of 'em (bunch of cuss words). I know I can't blame it on the FAST, yet, but I may never know how good or bad it will be. It is in my garage now and will get the 3.91, a rebuilt 727 to match the motor, TC to match, and a cam kit (or piece one together). Lunati seemed anxious to match it up. I'm going to try the 850 DP I have. It sure wouldn't work with the set up it has now.
I had a new '64 Fury and traded it for a new '65 Sport Fury, both had 383 hps in them. Both 4 speed and only change made was a high riser on the '64. That was over 50 years ago, but I remember the feeling both, especially the '64, gave me. This Duster is a "feather duster" to them. So, I'll spend the bucks and do it right. Too late to turn back now. Hey, I thank all those that replied to the post and if you have any other feelings about the direction I am going, please let me know. I am very confused about one aspect and that's the 727 and the TC I think the set up will dictate the TC, but if anyone has a recommendation or experience with having supplying a trans that would help get me to the end, I'd appreciate it. There's plenty of re-builders around, even here in the Ozarks, but I'm not taking it to, or buying one from someone that others on this board won't recommend.