What problems can I expect installing 1990 D44 rear end ,batwing,driveshaft,torsion bar into 1984 manual car.All info I can find only goes back to 85,

No different than swapping it from any other year.

Yep, the probable reason for the lack of info is that 84s (auto or manual) did not come with a D44. In 85, manuals started coming standard with the D44.

Otherwise as Jeffvette said, no difference.

You will find that the 4 holes drilled into the pumpkin (at the 5 and 7 o'clock positions) are larger diameter than the 84. The matching holes on the strut rod brackets are also small, matching the 84 case holes. Although the brackets are probably enough to locate the strut rod brackets securely, I do not trust it.
I always open up the bracket holes to match the later pumpkin holes, and use the later year, larger diameter bolts.

Thank you any driveshaft mods required if from 90 manual car?Also read that rear end assembly for 90 is 1" wider, any problems here?

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I'm not 100% sure on the driveshaft, but it was my understanding that as long as you are using the manual d/s it's ok. As far as the width, the total suspension has a different width due to the spindles/knuckles. The differential carrier should be the same width as far as the mounting points.

Matthew

I think you will also use the manual car c-beam, or redrill the holes on your d36 c-beam. Look here:

http://www.joby.se/corvette/mods/2001-0X11_diff/

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Unless you want to change wheels , shock mounting position and park brake setup ,you only swap in the batwing and diffhead keeping all your '84 outboard parts