I too am new to this site, and I am also putting a 454 in my 66SSconvertable. It is remarkable how much a person can learn by actually doing it. I learned more in the past year about my car, than I knew before that.
I like what both BigDave and Dadstoy said about your comments.
First of all it's a 454. Your not going to get much better gas mileage. Not even with a FI. It's 10-12, that's it. This is why I am going to stay with the Rochester Quadrajet. I found a site for a FiTech single port FI. It's all computer controlled on board. NO outside components controlling it. Only sensors. Plug an play, no adjustments needed. But I was told by a FI technician at a speed shop, that it isn't always that way, and if it needs it, you will need a professional to set it up. You can't do it yourself. That said, the positives about the FiTech are; you can use your existing gas tank with no mods, and your existing mechanical fuel pump with no return line, because it uses a small stainless tank in the front by your engine or fender-well that has a gas pump in it. If you go with any other style FI, you will need an electric fuel pump, most likely dropped in your tank, and a return line from the engine area to the tank. Therefore your tank will need a mod to add the return line hose. At least mine would have. For these reasons, I am going to rebuild my RQ with new bushings and it will be much less trouble than any FI.
Radiator? oh yeah. You want at least a 3 stage with 2 electric fans. You can get them from most places like Summit or a radiator shop that drop right into your 67 and bolt up to your existing core support. Don't forget the larger trans cooler if you are upgrading to a T400.
I didn't get the tubular control arms, but I did have my frame guy reinforce my control arms on the rear end. He welded a plate lengthwise the full length to make the "U" shaped arms into a box or square shape arm. Much stronger, especially if you convert to POSI like you and both did. I am using 3.53:1 gears so that I didn't need to by a 4 speed. These gears are low enough to use the T400 3 speed off the truck engine I had without the need for an OD.
And don't forget to get a Chevy flag 454 emblem for the fenders. (grin)