I went with the Professional Products Powerjection III fuel injection. Self learning and good to 600+ HP. For your engine I would get the larger 80# injectors and a bigger fuel pump like I am running.
I run a 421SBC with a decent solid roller and it idles like a kitten but screams like a raped ape at WOT. I have 11:1 compression with about firstname.lastname@example.org" and .660 lift. Engine makes a little over 675HP NA. Timing is 24* initial, with 36* all in by 3000rpms. I also have vacuum advance hooked up with 8* total advance under cruise and zero advance at idle.
The Powerjection III is an easy install and works with a stock intake. Even looks like a carb. I compared it to the FAST and Holley systems and it had more features for less money and was boost/nitrous ready out of the box, which the other two are not. I run a 200HP shot of nitrous with mine.
Listen to F-bird on the timing. I followed his advice and got my engine idling, cruising and WOT right.