1: there is a large tolerance in the bolt holes, and the locating holes in the bellhousing, so you need a dial indicator and base so you can center the bellhousing to the block.
2: you will need a welder to add the locating shims to the bellhousing.
3: you may need to grind on the bellhousing flange to clear the exhaust system and clutch linkage.
as you can see this is not a bolt in swap. take your time in centering the bell otherwise you will have vibration problems, and will wear out bearings and clutchs fairly quickly.
I put a McCleod scattershield in my 67 GT350 and kept the Z-bar. Had to cut a V-shaped chunk out of the scattershield to get clearance for the lower clutch rod. I also had my engine builder center the scattershield for me. There were some offset dowels that came with the scattershield that he used to center it. I was able to use the stock clutch arm but I had to install a fulcrum inside the bellhousing for it to pivot on.
While I was at it I had roller bearings put in the clutch pedal support (Mustang Steve, $85) and had Opentracker make me some Heim-jointed upper and lower clutch rods. Clutch action is really, really smooth.