We installed a Richmond 5-speed in our 67. It fits without any mods needed to the transmission tunnel and the shifter will come out in the stock location. To install it you need to reposition the transmission mount and they give you the instructions on how to do that. That's the only fabrication needed. You also need a 26 spline clutch and yoke and the two-sized universal joint that allows you to hook up to your stock driveshaft. The Richmond has a one to one top gear so, if you have a 3:36 or 3:08 rear gear, it will work well for cruising and the first four gears are lower ratios.
From what I have seen of the Keisler kits, they have everything you need to install their transmission already included and no welding is necessary. It sounds like an easier installation and I know of a couple of people who have done it and are satisfied.
Rich Lagasse