1970 Mach 1 4-spd into 68 coupe, easy fit?

I swapped my c4 to a T5 and the biggest issue you will have is getting a 68 pedal assembly. 68 is not the same as 67 because of the difference in the steering column crash function. It would be easier putting a hydraulic or cable clutch in rather than messing with all the old linkage especially if you have a late model block. If you are going cheap and using all those linkages and springs make sure you have all the parts before you begin. I did the swap on a previous stang about 20 years ago ( I was 17) and the return spring under the hood was not installed on the z bar and I went through a few clutches. Again if you go the hydraulic or cable route now you can easily upgrade down the road to a t5. You should not have any problems with the booster either old school or hydraulic. I do not think you will need to shorten the driveshaft.

It'll all fit, no change to the driveshaft. The clutch linkage as has been posted is the biggest hurdle. As for thr differences between the 67 and 68, that's only partially true. The 67's got a collapsible column in mid year. The early 67's used the 65-66 column.