Philip,
I did the upgrade to my 93. It's very nice and the gears are a good combination to wanting shorter gears but include a tall 6th for, as you say "motoring" on the Hwy. It's not very difficult, It's about as tough as a clutch change. You will need to upgrade the flywheel and related hardware & the later single disk clutch/pressure plate. Also you'll need to buy the plug & play reverse lockout kit that Comptech sells, or wire your own switch to to activate the solenoid which prevents accidentally selecting reverse while still rolling fwd. If you have a race car, I'd put in a switch. Otherwise Comptech's part is a better idea. It also comes w/ the 6 sp shift pattern plaque. I did the upgrade myself in my garage. The hardest thing is pulling the half shafts (drive shafts) from the gearbox, as the snap rings that hold them in work well. The rest isn't so bad. I have sold 6 spd gearboxes to several guys through Ebay on this site, so you should have good sources for info if you decide to do it. If you have a nice car, it might not be worth getting rid of it & "trading up".
Hope this might answer questions.
Take Care!
david