Fueling & Injection - might switch from carb to injection

right now i have a 403, D1SC, AFR 225's, EPP cam, carb-i have a GM intake drilled for injectors i would switch to, use a throttle body (4 hole carb style, not the stock style) and reuse my current carb hat and piping (intercooled)
i have an A1000 pump, and return style reg, boost ref up front, #10 feed, #8 return
i would switch to the FI reg.(return), and dead head a line to each fuel rail???
would that work ok, and what size injectors would i need, just guessing
maybe 600-650 RWHP
would the A1000 keep up?
not sure what system i would use, FAST or whatever, still looking at the most cost effective, i use an MSD box now to run the engine, i guess whatever i get would take over and run the whole thing
im pretty computer stupid, why i went with a carb orig, lol
i have a 4l80e run by its own Compushift controller, i would leave that as is
i have a GM computer, can they be made to work, mod the wiring harness,
or better off with aftermarket-not unhappy with the carb setup, just thinking i could get a little better management out of FI-hope all this makes since, lol

man I dont know if I can help but i can give you a bit of info on the engine management stuff as im still kinda goin through the same on my obs silverado swap. Ive done some research on this stuff and it looks like the factory ecu is the cheapest way to go because the 1 unit will control fuel spark and the tranny if desired. Painless has a universal engine harness for a bit over 400$ for the ls. With the FAST ecu you also have to use an ignition controller and they are both kinda pricey. BS3 will controlle fuel and spark is 2k plus! Megasquirt is affordable and i hear nothing but good things but it needs circuit board modding to manage spark. Hopefully this will help a bit

thanks, its looking a little more pricey than i figured, something like $2800
give or take a few hundred

MSII would prolly be the most economical route, but requires alot of user input, for the more experienced tuners its no prob. also with MS system, u can use the msd box u have now to fire the coils and let the ms manage the fuel. alot of people use mech.dist. with ms, so in theory it would be kinda the same thing.
are u wanting better mpg? is the carb. and tuneup tempermental on occasion?.
seems like those CSU carbs are tuned pretty good from the shop.

i have had around 10-12 Procharged cars with carbs, they all ran good, just thinking down the road trying something diff, i got the new motor pretty close to perfect, a little rich on the top, but thats a good problem to have, lol
prob. some power to be gained if each cyl could be tuned, i get a little mixture diff. between cyls, the left bank seems to run a little leaner than the right, so i have been tuning the right side, more so on lower rpm's