Looks nice, should be a fun swap. Certainly won't be many others around like it...
What are you planning to run for rear gears? I assume that B21 car probably has a 3.54 or 3.73 in it? Turning those big swampers may be interesting if it's got a tall gear in it, stock TD/M46 is 3.54 in a 7 series, and it's short enough that 1st gear is pretty limited but with those shoes I would not want it any taller than that.
Since you live in a hot part of the world, what are your plans for cooling? Common challenge for these, especially for mountain driving on hot days -- you probably will want as much radiator as you can get in it.
Will be fun to watch it come together, if it turns out like some of the others you showed above, should be very impressive!
