the fivespeed you had in the 280E was probably a fivespeed with an overdrive, fourth 1.1 and the fifth 0.8, it shouldnt have had that spongy feel thou, unless it was fitted later on.
afaik the fivespeed in the w115/w114 and early w123 had a iron house, and a aluminum bell housing, and
unless the first gear was downwards, and second up
it should be an overdrive, the 1:1 fith could be found in vans/trucks and was a close ratio box (or more like a superlow first)
711.113 is 1:1 in 4 and 0.8 in 5th
711.110 is 1:1 in 5th
later on in the w123 the aluminium 717.400 came fitted to the om617 and 280E engines, those had more of a spongy feel, and a underdimensioned bearing at the front, and thus not as great longevity as the earlier 711.113
and then there is the third fivespeed 117.261, wich also should be overdrive fifth as far as i know.
searching and paying for a fivespeed thats a straight fit is utterly expensive, you are better of welding another bellhouse to a w124 fivespeed, if you stumble upon a car, and the seller doesnt know what he has, it might be a good idea to take it
...he's a member on here. found his thread: http://www.mbclub.co.uk/forums/engine/177886-m104-e320-engine-w114-coupe-pictures.html
except that maybe its fitted when the car has a floor change rather than a column change so it's included for completeness? In other words you will have them already 
Part 30 I would guess is a rubber grommet? will check 
