The edelbrock I currently run is a 750 and has given no problems so far,but did require extensive re-calibration from the box.It was slightly lean on cruise when the 454 was stock,after the head and cam upgrade was massively lean on cruise and lean on power, to the point that the lean surge on cruise more like a bucking bronco,after the necessary jet,rod,and spring changes and a slight adjustment to pump shot I'm pretty happy with how it runs now.I had a smaller one on the 305 that was in the truck before and it seemed to be ok on it,after I swapped in the big block I stuck it on,and realized immediately how inadequate it was,seemed like no matter what you did it didn't improve anything,what you said about bleeds and emulsion tubes makes things clearer in hindsight.I think that carb would have been a poor match for a decent 327 or 350,it may have worked for a stock smog era 350.