I'm in the process of doing this to my 76 wagon. I got a set of pedals from a 74-up Pinto & they bolted right in. The clutch cable hole is already in the firewall. Swap in the bellhousing, clutch & trans. & that's it. T5 shifter requires a minor cut on the tunnel for the new shifter location. The cable needs a small home made bracket to move the cable an inch to the side. T5 or C4 yoke fit with the stock driveshaft. The neutral start switch must be bypassed & the backup lights need connected.
Search the archives & it's all here. I would rate it a 2 out of 5 in difficulty levels.