What size idler gear bearings do you have? The later MK1 cars use the larger size idler gear bearings as per the 4 synchro boxes. IIRC the early cars used 1" O/D bearings with the equal length idler gear shaft. Later MK1 cars used the 1 1/16" O/D bearings with the unequal length idler gear shaft. Housings for each are different externally.
The 1 1/16" bearings go with the 22A1288 commonised 3 synchro gear box case.
Flute's pic shows the later type. It has a depressed section around the middle of the flywheel housing. This should have 1 1/16" O/D idler bearings.
Around this time they also came with the boss for the breather for non S 1275 blocks.
IIRC my 66 S didn't have the depression. It was just flat and had the 1"O/D bearings. (Well it was 40 + years ago)
The MK1 stick is thin and chromed and didn't have the grease nipple under the centre front of the remote housing. A MK2 remote housing I have has the grease nipple. I modified my MK1 remote by adding the grease nipple at the front and also added a grease nipple to the cap on the anti-rattle plunger and drilled a small hole through the brass plunger.
Hope this helps
RonR