[WKB]

Sambo.

With the rear cover from the R33 attached to the S15 diff it should fit straight into the cradle. On the R32 they had to make metal bushes to replace the rubber bushes as the R32 does not have rubber bushes.
Once in the cradle you will see that the snout of the diff sticks out about 20mm further than the R33 diff due to the position of the speed sensor. If your tailshsft is not yet made no problem as you make it to suit, if it is already made there should be enough freeplay to slide the yoke further into the gearbox(this what they did when the S15 diffs were fitted into the other cobras).
When they tried to swap the drive shafts from the R32 diff to the S15 they found the S15 drive shafts had 1 more spline than the R32 had.
Two ways to fix this are 1. Get axles from a SX200/S15/S14 which should be about the same length as the R33. The R32 conversion didn't use this method due the potential cost of the axles. They went the second way and made an adaptor that went between the S15 drive shaft and R32 axle. There was enough movement in the CV's to fit a 8mm spacer between. This might not be issue if the R33 has the same number of splines on the drive as the S15 has.
Both the cobras that had this conversion were 4.6ltr quad cam fords, one with a T56 and the other with a T45. The outcome was the same, quiter at highway speed, easier to maintain highway speeds , better fuel ecomony and able to us first gear for more effectively.

If you are going to do this mod replace the rubber bushes with metal bushes. Under hard acceleration the rubber ones can be damaged.

Warren