There are some Economaster versions stamped List 9117 on the choke horn. They have a funny 8 slot 'turbine' style venturi booster which looks very interesting!
They are actually more like 320 cfm, but the same size as the 350 cfm 7448.
Oh, just to amend the above post, the 500 cfm carb is the List 4412. The 350 cfm carb is List 7448.
But hey, I won't hen peak someone for getting the numbers da wrong way awound! Anyone who is nice enough to hand out the inforamtion desserves a handshake, its what makes the site so much fun!
Really rare is the List 6425, a 650 cfm Holley with Dominator style crome air horns reaching for the sky. These have 62.5 thou over throttles and venturis for 1.75" throttles. Great carb for a really hot in -liner!
The easiest way appart from the list numbers is to look at the throttles and carry and carry a rule. You'd be supprised how many carbs have been fiddled with. Yu can fit all sorts of 500 baseplates to the 350 , or mix and match some of the 280 cfm stuff from the AMC 232 and 327 V8's.
If its 1.6875", its the 500. If its 1.5, its the 350.
Old Internationals and AMC Rambler variants used an early version of the 350 with even smaller throttles.
The 280/320/350/500/650 carb is called the 2300 seires, and for the I6, its the best carb for the money anywhere!