Low car diet
Join Date: Aug 2007
Location: Corvallis, OR, USA
Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
You'll need new shifters and brake levers. One combo would be drop brake levers and bar-end shifters. Another would be integrated brake/shift levers ("brifters").
Think the rear derailleur matched to your 5.0 grip shifters will only be compatible with SRAM brifters (don't think they made an 8-speed though). You could always switch the rear derailleur out to a Shimano to widen your options.
Another consideration is brakes. If you have V-brakes, you'll need to 1) get brake levers meant for these V-brakes; there are only a couple out there (you won't be able to use brifters), 2) get an adapter for the V-brakes, or 3) switch to cantilever brakes.
The cheapest option--if all you're looking for are the drop position for part-time--might be some drop add-ons I saw at my LBS. I imagine you'd want a shorter MTB bar for it (ie, cut your existing one).
What bike are you wanting to convert?