BW78 came in Falcons.. and they are wide
Or do you mean the BW75 used in Pintara/Skyline ?

Commonly called a 78 but thats not actually true
Same with Commodores... they are also a 75 but often called a 78

Easiest way to tell is check crownwheel for markings... 0575 for a 75 series... 0578 for a 78 series
Though the LSD centres interchange

Pintara/Skyline is 1440 from memory uncut

How much wider is an uncut bw78 than the stock rear track wiidth or diff width drum to drum?

Is it. 3 inches per side or 3 inches total?

Also are h 190,s similar width?

Reson being is I'd like. LSD eventually but not the expense of cutting one down, with my hack car better just adding flares and cutting the rear arches up a bit.
Also means can widen front track possibly to match.

I understand bw68 has a long and short axle so drive shaft may to be centered in the car? Is that correct.