Ok, first thanks alot everyone for the few bits of info gathered so far. I got under my car yesterday and took a measurement of the front portion of the driveshaft. From the centre of a bolt holding the carrier bearing to to the forward end of the u-joint ear thats welded to the shaft (not including the yoke in the tranny) I have 21 15/16", nearly 22".
Could anyone with a 4 cyl auto Ob measure theirs to see if it's the same? This would nearly 100% confirm that a 4 cyl shaft would fit, just a different part number due to being a "heavy duty" bigger tube and possibly bearing . Thanks alot and I hope this works. Vacation starts this Saturday.