Go to a clutch specialist & ask for a heavy duty clutch to suit an A14. This is what I used for years with no problems other than normal wear. this should give you a slightly heavier clutch pedal, & better clamping. As for the flywheel,use the A12, as they are usually slightly lighter than A15 flywheels.
The longer throwout bearing housings are usually needed due to the greater distance from the front of the bellhousing to the front 'bulkhead' of the A14 4 speeds & 5 speeds, plus that horrendously thick & heavy plate that goes between the block & the gearbox. I usually take this plate out & use the clutch cover from a sunny auto gearbox, which has the larger holes for the 8 mm bolts on the A14 boxes. I don't know what using the longer bearing housing would do, probably only cause the clutch pedal to contact the diaphram a bit sooner, but then again it might cause the diaphram to go overcentre. I do know that putting a short housing in when you should have used a longer housing causes great distress, as you then have to pull that *****N* gearbox back out to fit the right one .