I'm not a Capri man, I'm an Escort man, but based on the symptoms you are describing, I would put it down to 2 possible scenarios, one of which has already been discussed, that being a bent clutch fork causing the problems described.
 
The other scenario relates to the pivot point end of the clutch fork, the opposite end to where the clutch cable connects. In an escort, I believe with Pinto motors and not Kent, there is a steel block located between the fork and the bell housing in order to correctly place the thrust bearing assembly in position relative to the fingers on the pressure plate, as well as insuring correct geometry in the clutch fork movement and also places cable adjustment within a usable range as designed from factory, meaning the adjusting nuts should sit somewhere close to the middle position, and not over extended, leaving you with little room for adjustment. If this block between the fork and bell housing is missing then you end up with the symptoms you describe. Along with the steel block, a special bolt is also used in order to hold the clutch fork and block assembly in place.
 
Just a thought. It may not apply to your Capri.
 
Chuff

Sorry to chirp in guys but from the start inside the car you have full travel of the clutch pedal? And in the box your getting full travel negating a couple of mm deflection if bent but you are saying your missing 70mm of travel if that's correct it must be the wrong clutch cable not giving you your adjustment.
Try applying the clutch pedal and tell us how much movement you get on the other side of the cable as that is your travel. Then work out how much travel your fork needs to work ( not much) and make sure you have the tolerance to make it work. I reckon it's a cable issue not allowing the adjustment.
Also I didn't know of a difference in flywheels between the Dport and oval port I will need to check on that.

Are you saying that the clutch starts to disengage when you have the pedal only 2" from the floor, thereby only giving you 2" of travel?
 
If so, grab the clutch cable outer on the engine side where the cable thread goes through the bell housing and pull the cable outer as far as you can towards the front of the car until it stops. As you do this the clutch pedal in the car will lift but that is what you want, and there will be resistance as there should be a spring between the clutch pedal & pedal box. Once you have pulled the cable all the way, are you able to position the 2 nuts for adjustment and leave a gap of around 2-3 mm between the nut and bell housing? If so, then lock them in place and try your pedal travel. If you can't lock the nuts as you've run out of thread on the end of the cable, then you must have the wrong cable, as the outer is too short. Similar scenario occurs if you smash & remove the plastic/rubber insulator on the cable where it goes through the firewall. Cable outer length becomes shorter and limits adjustment.
 
I don't see how it can be anything else.

Is it the MK3 V6 capri cable?  they have a big bushing at the top http://www.ebay.com.au/itm/FORD-CAPRI-3-0-2-8i-NEW-CLUTCH-CABLE-/361313305671?hash=item541ff38447 this might give you grief.  They are being sold off as suitable by a few of the specialists
 
A MK1 capri cable should look like this http://www.ebay.com.au/itm/NEW-CLUTCH-CABLE-QCC1014-FITS-FORD-CAPRI-MK1-2000cc-V4-1968-71-/191678519332?fits=Model%3ACapri&hash=item2ca0ee1824 

Strange how this Clutch Saga is prevalent !..........When I found my Capri some 4 years ago, I drove it back to Mornington from Ballarat and it drove like a dream (AFTER SITTING in shed FOR 15 YEARS IYDMU!!!!).......no Clutch problems at all !
 
Pulled Eng & GB out , overhauled engine, and next item was to replace all Gaskets and Seals on a very leaky box thanks to some yo-yo putting in Selector Seals that were 100% useless and had a 1mm gap for oil to slush out !!!........they weren't worn out; just wrong as proven by eye/calipers and part number still on them !......lucky I filled Box b4 leaving Ballarat, and she lost 1/4 of fill by the time I travelled the 200km back to home, with no damage..........
 
.........not satisfied with leaving well enough alone, I had to self-criticize the amount of "slop" in the Primary Input Shaft which wasnt due to worn bearings. So I "spaced" up the gap between the Front Cover/Thrust Support and the Main Fr Brg Circlip just so there was 90% of "slop" removed...............BIG MISTAKE !...........now cant select ANY gears unless I double de-clutch which I havent done for many decades.............it wasn't pretty !
 
:-(  ..........back in the shed till I have time to r&r GB and remove offending spacers !.........BUGGER !