I have allot of experience in both the Holley Tri Power (Chevy speak) and Six Pack set ups, both small and BB set ups.
Get your original carbs rebuilt by a reputable rebuilder that knows what he is doing. As far as the new holley six pack or tri power carbs that have been sold for the last 20 years or so form Holley, they do not have the proper metering plates, and they need some other minor work right out of the box to get them running in top shape. Yes, they will run OK out of the box, but the new ones aren't set up like they were back in the day when sold on tri power or six pack equipped cars. This includes most, it not all the complete and new holley six pack setup kits (carbs, air cleaner, linkages, the whole deal) that have been sold over the last 20 years or so.
Holley lost their in house historical and tech knowledge on six pack/tri power cars decades ago. Not bashing Holley, but it is the way it is.
Most of the reputable rebuild guys out thier that handle tri power/six pack setups realize the deal.
I would get them rebuilt as such.