Having mounted the clutch MC on the firewall of my own car, there’s less room than you think. The firewall is not flat for a large area, there’s the indent for the brake MC, a stiffening rib, the emergency brake cable, etc all in that area. Plus you need to make a bracket to hold the clutch MC back there to go straight through.
And here’s all the space you get on the other side
View attachment 1716097469
Easy right?