For the most part I agree with most of what Jim said about conversions. I don't see the reason for going to 5.9L Cummins when a good engine can be had in a drop in situation with say 6.5T. I have a 1971 Ford Bronco with a V-8 302 in it. The darn thing loves it's gas. Now I've run across a guy who dropped a 3.9L Cummins in an EB (early Bronco) and he has all the power he needs and get 28 mpg's mixed driving. With the 32 gallons of tanks I have on mine that would give me about a 900 mile range more than double what I have now. I think a 6.5TD would be a tight fit in the old EB but I think a 3.9 would tuck in very nice from the photo's I have seen. In fact I have located a 3.9L enionge and 5 speed OD tranny 3 hours away. I'm thinking real hard about it.