Weber measurements needed, please...

I could really use a measurement from someone with the Weber conversion kit.  I want to replace my holley w/ a 38/38 but am limited height wise and would appreciate a full height measurement from manifold to aircleaner top.  I have a little over 7" to the hood and with that adapter I know it would be close!  Thank You-   *SIDE QUESTION*-Are these progressive or synchronized?  Any info or tips on the swap greatly appreciated

The 38 is a synchronized linkage.  The 32/36 is progressive.  If you're going for economy, stay with the 32/36 or another carb like the 2100.  Realize that the 38 will require engine performance mods in order to provide satisfactory service.  You will need a cam, intake, and exhaust headers, in order to make the upgrade pay off.  Also, the jet kit will probably be needed to optimize tuning if you're running a cam.

You need some "real "Webers:

I'd consider a rebuild of the Holley, plus a good cam upgrade.  I'm assuming you've got the Holley 390, which has great potential, equal to the Weber 38 by all accounts.  The 38 isn't going to flow more than the Holley, though Clifford swears it out performs the Holley.  The Clifford numbers are all at RPMs that my 258 would never survive, and at the normal driving RPM there can't be that much difference.  Not $500 difference, that's for dang sure.

No one could force me to use the Comp Cams recommended springs in anything but an all out drag engine! Way too stiff for anything but high rpm performance. The MP springs are stock Magnum V8 springs and are just a bit stiffer than the 4.0L stock springs -- plenty good for up to 5000 rpm. I'm using a MP cam (the second one -- kicks in at 1100 rpm) and love it. It's a 4.0L cam, but will work in the 258 -- but you'd have to use an electric fuel pump. The Comp Xtreme cams are good, but as Pdok said, 0.480 or under lift so you can use stock type springs. If you like a profile Comp has but don't want the lift they will custom grind you one with lower lift. The only difference will be lower high rpm power, which you won't be using in a street vehicle anyway. 4000 rpm and under you won't notice a difference (probably 5000 and under!).

You definitely need a 2V carb. As mentioned, the 38/38 is a bit of overkill. The popular 32/36 would give you a noticeable increase in power without killing your economy at low/cruising speeds. That or a small Motorcraft 2100 or Holley 2300. The 1V carb is about 150 cfm, the BBD 2V about 195. The small Motorcraft and Holley are around 350 cfm.

The mentioned Holley 390 is a four barrel. That and an Offenhauser dual plane intake would be a great combination for power and economy. I'd stay away from the Clifford intakes. They are great for mid to high rpm performance, not so good for low rpm. The Offy DP is hands down the best for that, but can only be used with a 4V carb. It could be used with a custom adapter with a progressive 2V like the 32/36 with good results though. Would have to use a throttle cable, and if you have an auto transmission the linkage would likely have to be replaced with a cable (Lokar makes a cable kit for AMC/Mopar auto trannys) and may take some finagling to work then. Stick shift is no problem!