It's turning out my rebuilt '57 bird 4150 style holley(1273 ECZ-V) is kind of a mutt, biggest issue i see is that it's using #109 butterflys which should be on something like a 600 cfm. It already has the right linkage and seems to cover all the passages right though so i'm almost debating on using it. Is this going to cause issues? I kind of feel like having a step between my body and base plate might cause idle issues since the idle mixture is in there.

Holley doen't make base plates for the smaller carbs as spare parts,The only chance you have is to find a cheap 465 or 390 cfm to use as a part giver!

The Venturi determines the cfm along with the base plate. A 750 plate could actually help. You can buy new bases on Summit by one of there suppliers Quick Fuel comes to mind.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I think i have 4 450cfm's and 1 more t-bird carb so i'm good to go there, i was just being lazy and didnt want to have to rebuild stuff