switch over to 4 barel and headers

Holley carbs use side hung or center hung bowls.Yours appears to be center hung (I prefer them)the metering blocks are normally not used on the secondary side when it is vacum secondaries, but they are always on double pumpers for fuel metering adjustments.You can keep them on with vacum secondaries for more secondary metering control, or you could remove them.I would check to make sure the bowls would work without the blocks, I'm not sure if they're interchangable?You would definatly have to change the bolts as they are different lengths.Does the rear bowl have an accelerator pump like the front?If so it was possibly a mechanical secondary/ double pumper.