'66 4-Jet vs '65 AFB for a fresh '66 407 Nailhead, which is better and why?

Took the consensus of advice and now looking to replace the 4-Jet on my freshly rebuilt '66 407 Nailhead, mildest cam/springs upgrade with this 3921S AFB. I did list some of this on another thread but thought you should see it here also. Can't seem to locate any specifics on the internet of what this carb had originally, somebody has got to have the book out there!

Decided to freshen up the AFB and upon dis-assembly and cleaning found 120-256 primary jets, which fit (with slop) a 5/64" drill bit, secondary jets are about the same size but unmarked, both step up rods are bent and one is longer than the other. They measure .080/.065, the pump discharge check needle is completely missing, and the fuel inlet screen is missing. The primary shaft has a little play in it, .010"? There is also some AL corrosion on the bottomdue to the exhaust gas getting through the base gasket, no SS plate was found when the carb was removed from the engine.

What have I got here? And what jets/step up rods should be in here, or what would you guys recommend considering today's pump gas? I try to run only Mobile 1 Premium with a lead substitute and high zinc oil.
This is not a race car.

Thanx in advance for any feedback!

 

Chassis manual has info on jets and rods, start there...

 

http://65gs.com/65 Buick Gran Sport...K SKYLARK GRAN SPORT SERVICE MANUALindex.html

See page 46 for carburetor information.

Know you are on a budget but recommend finding a good carburetor rebuilder. Kits are available. We're some on eBay recently if you want to do it yourself.

Dan

 

i had about a grand in my set up i paid more for the air cleaner then the nos carb