I have a slightly modified 289 in my 67 and I tried a vacuum 600 holley and a electric 650 edelbrock double pump. I got lucky in the fact that the guys who have been helping me plan out my mods at the speed shop and parts store had spare carbs they let me try running on the car before I bought.
Really liked the performance on the 650 more so than the 600. I've been told a few times that I'm waisting extra gas, but I'm still happier with it.
Mods are edelbrock performer intake, comp cams camshaft (can't remember the specs right now) - kept it street size though, new lifters and double valve springs to match the cam. Alum. rockers, long hooker headers, dual flowmaster series 40 exhaust and and MDS ignition system. I'm also going to add an X-pipe to the exhaust. Had a valve job done on it as well.
Never dyno'd it, but I might once I finish the work and am actually home long enough to do so.