Check it out for yourself... http://www.geocities.com/z_design_studio/
Enter your setup and see for yourself what the results will be for the different trannys. The 82 has a taller 5th gear for crusing but if I remember right, the 78 will give you a bit more low end off the line if you're using the original differential for your car, compared to the stock 4 speed...
I went with the 82 5 speed with a 4.11 diff to get what I wanted.
and I suppose if you match the 5-speed to the same year engine it might be a somewhat easier install...look it up in the archives here...like Jerr says: it all depends on what performance you want...good luck )