I totally get the logic looking at stock TBI setup. The parts aren't as easy to get anymore. The sensors are, but the actual throttle body unit is no longer supported by GM. The 454 unit is not the same as the much more common 350/305 unit either. Holley was making replacement TBI units at one time and I'm not sure they are anymore. I used one on one of the employee's trucks at work and I'm fighting a driveability issue with it and the standard GM TBI IAC and TPS sensor don't fit the Holley unit. There are some good rebuilders out there that I'm probably going to have to get a rebuilt OEM unit to address the problem. The point I'm getting to is even the newest TBI system GM put out is 25 years old. You might want to look at a new harness and controller set up to your specs by somebody like Howell. Or research some of the aftermarket EFI systems that have come a very long way in a few years. Holley Sniper, MSD Atomic and Edelbrock Pro-flo are some of the options. I've got a couple of buddies from CK5 that have put the Pro-flo setups on their squarebodies with excellent results. Simple to set up, self learning and don't require an engineering degree to run.
It's worth looking into and comparing pricing on refurbishing an OEM TBI system with new harness to a new aftermarket system.
Oh, when I said old school TBI, I was meaning I was going to be looking at a Howell setup, not try to piece one together as you are right, 454 ones are hard to find and likely will need to be rebuilt anyways. What I was after is being a stock type TBI, sensors, injectors, etc. are stuff I can buy off the shelf in most parts stores around the country. They are also fairly simple to troubleshoot in the field.
As for aftermarket setups, I have a FiTech EFI (though not installed on anything) and have been on forums since these "all in one" EFI systems hit the market. Sadly they have been totally hit and miss on reliability and trying to figure out what part you need when you walk into a store is difficult. Also hard to troubleshoot. For my hot rods/classic cars which are likely to stay more local and always on a paved road, they could be worth the risk of failure but for something that is going well off the beaten path, a basically stock type TBI is likely going to be much more reliable. Plus the GM type TBI systems have a limp home mode, which I have not seen with the aftermarket ones.
That all said, nothing has been decided. Heck, I might throw on the FiTech since I already have it. LOL What I am thinking of doing is, using a standard squarebore intake manifold, using an adapter plate for a TBI. In worst case, I could yank that off and throw on a standard carb in a parking lot and likely get me on the road again. That could be a worst case scenario.