I've rebuilt Hollys many times.The Carter types with so many different jets and rods if you are trying for maximum performance can be a hassle unless you have been doing it a while.
However a stock replacement of components in kit, is not too hard or hard at all depending on.......
The cleaner is still around for the body and such. You have to immerse the carb in it and it is murder on skin clothes and pretty much anything not metal.
The throttle shafts sometimes had bushings and if they are loose they can be replaced but not worth it.I've seen the blades and shafts messed up ore times than not. No bushings and worn shafts body where blades contact, you could buy the base plates with throttle assemblies etc from Holly. I don't know waht is available now. Often times I've seen carbs rebuilt but the shaft clearance and blades, worn and loose and it was a waste of money.
A new carb is perhaps the est bet but not the cheapest.
The Throttle body injectors with computer or processor is a great deal.
Since you have a big block the four throttle body is what you would want.
The factory can tune the processor so I'm told. And with a laptop and manual you can find tune it. A higher pressure constant flow electric fuel pump, and return line will need to replace the mechanical pump for the carb. I'm making assumptions as to what you have. You will get easier starting, no vapor locks, and better performance.
I would contact Holly directly for specs out what you need. Probably have to buy through a Retailer though.
These are just my opinions. Others perhaps have better.