I'm really not 100% sure if it will or not, but if it fits on a 350 throttle body, I'm sure it will fit on a 454 throttle body. You can go through my write up on my truck thread, the 454 throttle body is just slightly wider in OD where the intake hat fits onto the throttle body, and the factory hat has to be "forcibly persuaded" onto it with light tapping from a wooden block or rubber mallet. Also I dont more reading after I performed the swap that some people have actually knocked the lip off of the 350 throttle blade, theoretically achieving the same result without having to buy another throttle body. But without a doubt, the final decision is yours rather you want to do it or not.
Also if you dont want to deal with tearing throttle bodies apart, and swapping them, I could perhaps put together plug and play throttle bodies if one were interested in this
And on the headers, in my opinion, I wouldnt go with shorties, but I would rather go with mid, or long tubes due to the gains throughout the powerband.
But shorties do have their place, especially if you already had an exhaust done, and want something bolt on, and shorties only seem to have an increase in low end torque, and I havent heard too many people claiming increased fuel economy with shorties, but mid or long tubes seem to have a consistent gain in fuel economy. But you'll have to have another custom exhaust put in once more