differential

[87supraguy]

I have an 87 na with a locking rear differential my question is, is the non turbo lock diff. the same as the turbo diff? i have to replace my diff anyways but i also plan on doing the turbo swap so want to make sure i get the turbo rear end. also was wondering i found a steel one piece drive shaft that weighs half as much as the two piece stock drive shaft it's $300 hundred buck aliminum i think was $450 and weighed a 1/4 less than stock would one of these be worth the price? can i get one cheaper newhere else?? one last question while im at it. i heard that if you do the swap your factory tach doesnt work is this true?? if so is there a way to wire it so it does work? Plan on doing some work in the next month or so so when the snow is all gone i can get cindy (my car) back on the road im excited and cant wait!!! Thanks