Overdrive is great if you intend to drive the car on the highway, regardless of how you get there. I do not have any experience with the Gears Vendor OD but hear good things about them. As noted above, the 5 speed requires some minor mods to install but this is a standard swap and not a big problem. Either solution beats not having an overdrive gear for cruising without going to a 2.76 or 3.23 rear gear.