I did the same type of swap in my 74 Scout. If your 68 trav. Is anything like how the Scout is mounted, it's almost a direct bolt in. I had the 258 straight six, and installed a used 90 4.0 heep motor. The 4.0 kept the oem bolt pattern for the motor mounts that the IH 258 motor had. Heeps used the same motor back in the day, and the 4.0 was the direct replacement. It even has the same transmision bell housing. Only draw back the 4.0 motor has, is no provision for a mechanical fuel pump. Not a big deal since you're going efi.
Hope that helps