If the LSD is the small axle variety (23 spline) then you are fine. Take the nose of your T18 diff housing, LSD centre and 4.1 crown and pinion wheels to a diff specialist and get them to fit it all. Shimming up diffs is important and apparently complex and time-consuming.
Then drop this whole unit into the rest of your T18 diff housing, throw in your T18 axles and tailshaft and go enjoy some drift.
Hen
PS, just noticed, as for whether the TA22 ratio fits the T18 housing, I'm not sure, but I'd be pretty suprised if it didn't.
PPS, don't mix and match crown wheel and pinion pairs.