hey blkmonday; Bowtie is right on-- QJet is something that GM just did right.. they threw it on everything from a baby 262 to a Poncho 455, and it took it.. and that 425 of yours probably puts out some under hood temps, so the spreadbore carb would better suit your big block and manifold.. and his option of the AFB or ThermoQuad is another good option for an econo carb (like a Qjet), until you mash the pedal, secondaries dump, and that 'waste gas and go fast' becomes the option..
but seriously, while i would recommend the Q or AFB, i have used and liked the squarebore edelbrock's.. you didn't say what series, but even the smallest (1403?) 500cfm manual or electric choke is probably more than enough for your limited street use.. you mentioned a few years ago you had it timed and 'dialed in', and i am sorry that your shop did not elaborate why they disliked performer, but if ever their was a close to "plug n play", it would be the performer.. while it will limit the Super Rocket 88 you've got, it is still powerful enough, and a fuel saver, and (nothing against Holley, i love them too); once it is "dialed in"; your done, no power valves blown, leaky fuel bowls and buna tubes, etc..
before you spend $300-400 for a new performance carb (and yea, if it were mine, i would be gettin the 1903 edelbrock Q, BUT-) you might first just change fuel filter (you mentioned you never fired it up over winter), spray the carb full of Berryman B-12, buy some B-12 to dump in the tank, with some 91+ premium, and then think about a $20
phenolic spacer from Mr.Gasket or TransDapt; or even a $2 piece of pine (racers were building spacer/gaskets before speed companies caught up in the 60/70s; don't believe me? go to your jegs and search wood carb spacer) and some extended studs from Fastenal (right there in stratford; or the nutty co. guys down in milford); as i think the biggest hinderance in the carb (you mentioned you were never 'too thrilled') is partial vapor lock.. lift it away and separate from the massive heat of the block to allow the fuel to come in more cool and dense; and the berryman should help get some varnish out, and i am sure the filter is gunked up after six months of sitting..
-- while i am with Blue Bowtie as far as eventually going bigger to either Rochester or Carter; you can still get life out of that 500/600 (1403/1406-7) cfm Edelbrock, just lift it a little; .5"-1" you should see crisper response, more stable idle, no loss in mpg (unless foot gets heavy, haha) hope this helps..