I want some opinions if this is really worth it.

If I could upgrade to an 83 LSD rearend and front struts with the accompanying brakes into my 79 SA for around $200 should I?

I don't really have any plans on upgrading the engine so I will stay stock except for a future RB exaust.

 

I would definitely do it for that amount of cash.
You will have not only the advantage of having a LSD but 4 wheel disk brakes.Also will have a better choice of replacement struts on the front.
IMHO it is well worth $200.00/ :-)

 

Since the stock rear axel ratio is 3.909 and I'm putting in a 3.933 from an 83 rx7, how much is that going to put my speedo out?

 

Negligible; It'll read 0.614% higher than usual.

IE when you're doing 60, it'll read 60.3684 MPH.


You get more error from having worn out or new tires... Or having different air pressure...

 

If you do any sort of performance driving, the lsd alone will be worth it. Even if you don't, you might consider upgrading the car for future resale value. 200 bones is a great deal...

 

Remember that the brake line fittings are different between the 79 and the 83.

 

..and although it'll be trickier around corners, two wheels will get you up a steeper incline on snow days...