I would personally stay away for 3.0L V6 Ford's as I have rebuilt auto-transmissions for Ranger pick ups in the past. 3.0L V6's tend to use different bolt patterns on the bell housings so lining up a 3.0L engine to a 2.9L trans may not work or vice-versa. But the 2.6L, 2.8L (old Ford V6's), 2.9L (slightly more modern) and 4.0L would be a better choice and should have the same input shafts. The added torque from a 4.0L would be beneficial but necessitate upgraded components in the trans which can be bought through a transmission parts supplier. But if your going with a manual transmission behind a 4.0L; I would definately upgrade the clutch, pressure plate, throw out bearing.