Like most of the others you probably wont like the engine you built for daily driving if you want 400HP with small cubic inches. A 393 or 408 would be the way to go if you want a daily driver if you want that horsepower. More cubes means more torque and thats what you want in a daily driver. For a daily driver I would keep the cam intake duration under 220 at .050" If not your engine won't get you around town to well below 1000rpms where you might be driving to save some gas. People typically go to big on a cam.
As far as the AFR heads I say get them if you really can. I did a lot of looking around and those heads usually out perform other common aftermarket heads through the whole entire RPM range and they are not all that expensive.
If you can't find a shortblock that you like you can always get your own made. You might even be able to get short block made with better components if you get a local machine shop put it together. Look at
www.adperformance.com. They have great deals on good rotating assemblies and the best deal on AFR heads. Get 165's for a 351 and below or 185's for a 393 or 408. I would also recommend low expansion forged pistsons. There are not to many out there but SRP makes them.
I looked a long time for a crate engine for mine. Never found anything that I exactly liked and they were expensive. I know mine is better than the crate engines I found and it was actually cheaper getting all the components and having a REPUTABLE machine shop put it together.
As far as fuel injection, I sometimes think people over value it. They think it will give them huge increases in gas mileage when they usually pick up very minimal gains.
You will always have axle wrap with torque. There are very simple aftermarket things to eliminate this. As far as rear wheel HP look at about 30% parasitic loss in a Bronco. So if you have 400HP at the flywheel you are looking at maybe 280 at the wheels which is still pretty good.
