Hard to say from the pics, it could be a mix of what they had lying around, late s2 does have plastic CAS, it hasn't got the neo ps pump.
As you say see if it's got the drain at the front of the head, might not matter depending what parts are needed
A lot of mechanics are concerned you don't have all the parts needed and being stuck with the car while the missing parts are sourced, also a lot just don't want conversion work
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As Murray says find someone that's done them before
Email LTSA with the previous kms, the new kms, why you swapped it and a receipt for the new cluster.
It'll still show inconsistent speedo on Carjam but will be legal, Auckland Instruments or Robinsons could probably wind it forward otherwise.
There is a 5 speed but by the time you found one and then swapped the font half of the casing or made an adapter it would've been easier just to get a 25 box
Vee is atmo, dual is atmo, plumb back or 50/50, if the car is pretty std and runs an afm you really want plumb back, if that's the case why change the std bov
OS88 is the 6 speed sequential, not a gear kit for a standard box.
OS does a push/pull converter for the 33 box which would be the easiest way to do it.
The gear kit works with the factory gearbox parts.