It should look very nice in that color, I did a Celica Ra28 in ford blaze blue, very similar and it looked delicious.

You best go the Mazda box if possible as the only other speedo sensor you could run would be off a wheel sensor or see how the APV vans do it on the latest suzuki APV they run a slanted 1.6.

Youll need to get someone to use the 929 bellhousing and machine it about 2 inches to allow the same amount of thickness on a sierra bellhousing.

Im going traumatic (well improved internals and fully manualised) off a Vitara bellshousing as Im running the 1.6 vitara motor. I was going manual but got so used to an auto recently on a Merc coupe that I love the comfort and ease of not using a clutch. I know the Merc box is a different animal but trimatics internal mods have come along way. I also have an auto 3.4 ratio alfa romeo diff with alloy housed LSD which has to be shortened and hopefully run pintara disc and calipers, axles and outer section of axle tubing.