First thought....are all of the components (engine, trans, steering etc) installed now and the clutch actuation part is remaining to be solved? What type exhaust system you running? These can be a "fitment" issue too.
It's Ok to "think" ahead, but, very foolish to "purchase" ahead. How many stories have you read here regarding folks buying parts and 5 years later or longer they go to install and they don't fit or some other catastrophe. The clutch actuation part can be problematic even when all is installed. When I converted my C4 to T5, available at the time (2010) was the cable, McLeod, and "Z" bar. The hydraulic slave system was still a bit new. I chose the HD rollerized "Z" bar as it was not complicated. There are a number of success stories here with the hydraulic slave system. My '67 eType runs a factory hydraulic system and is very smooth acting. Yeah, headers, in themselves, can be a challenge for clutch systems.No, car is totally disassembled awaiting paint. Have engine and transmission are on order but have NOT decided on headers and exhaust yet. I have about 5 months to solve remaining issues. Still pretty much a blank canvas and will be able to reassemble in a way that make works.