I am putting in a 1992 chevy 350/700R4 combo in my 1973 vega this spring and have a question that someone might be able to answer. I am wanting to leave it throttle body injected but want to make about 300 horses with it. What cam profile and hyperchip should I use to achive this. Do they make bigger injectors for TBI? If it can't be done with the injection then I will just go to a carb set up. I know how to make sick power with a carb!!!!! Just not so much with the TBI.  

you might want to check into 454 throttle body....and bore you sbc intake to match...there were aftermarket tbi sbc manifolds also

there are a lot of aftermarket throttle bodys that have significant larger flow injector numbers..

you might want to talk to jim linder his shop in gasoline alley...as he has a charted the flow rates of tbi injectors... as i recall....  

I currently run a 496 with a TBI in my tow vehicle.  It's a full roller motor and the 454 TBI has been bored and sleeved to flow around 1000cfm.  Now with that said, forget an aftermarket chip company.  Take a read over at thirdgen.org forums.  These guys are running TBIs well over 300 hp with a laptop and some very reasonably price tools for a diy type on a budget.  I use a laptop, wideband O2 sensor from Innovate Motorsports, and several odds and ends from Moates.net to program my efi, spark, shift points, etc on the fly.  It's awesome.  The chip companies won't be able to get anything out of your setup compared to what you can with a custom tune.
waynep712 is right about the throttle body being bigger on a 454, but go checkout the DIY PROM section of thirdgen.org before you spend a penny.  You may be fine with your stock TBI and maybe some injectors.  

Thanx for all your help.