Elaborating on what Dave has said:
1983-1987 6.9L IDI (Indirect Injection) diesel designed/built by International
1988-1994 7.3L IDI diesel designed/built by International
1994.5-1997 7.3L Powerstroke turbo diesel designed/built by International
1998-2003 7.3L Powerstroke turbo diesel designed/built by International
2003-2007 6.0L Powerstroke turbo diesel designed/built by International
2008-2010 6.4L Powerstroke twin turbo diesel designed/built by International
2011- 6.7L Powerstroke SST (single sequential turbo) diesel designed/built by FORD
The IDI 6.9 and IDI 7.3 diesels are very similar with the major change being the increase in displacement/power which I believe may have been in response to Dodge introducing the Cummins diesel in their trucks. If I remember correctly 1992-1994 trucks were turbocharged but remained IDI
The 7.3L Powerstroke turbo diesel engine introduced computer controlled direct injection to the 7.3L with new cylinder heads and supporting hardware.
The 1999-2003 7.3L Powerstroke saw revisions to the fuel lift pump (frame mounted electric vs. the old engine mounted mechanical pump)
The 6.0L Powerstroke was a clean sheet design that was developed to meet stricter emissions standards. It introduced EGR (exhaust gas recirculation), VGT (Variable Geometry Turbo) among other things to produce more power, less pollution, a broader power band, and better fuel economy.
The 6.4L Powerstroke was a MAJOR redesign of the 6.0L with with very few items carried over. This engine was also a result of stricter emissions and more importantly to right the wrongs of the 6.0L I found an article somewhere a while ago that said what carried over but it wasn't more than a handful of parts. The 6.4 introduced twin turbos, piezo electronic injectors with high pressure common rail fuel supply, the DPF (Diesel Particulate Filter) and the DPF "Regen" which cleans the DPF of soot on a frequent basis.
The new 6.7L is a new design by FORD because they basically got in a cat fight with International over the warranty issues generated by the 6.0L and because yet again new emissions standards. This truck debuts, UREA injection, SST (single sequential turbo, two compressor wheels and one exhaust turbine wheel on the same shaft) and a completely reversed intake and exhaust flow arrangement from the conventional engine.
So lets see...
The 6.9, 7.3, and 7.3 Powerstroke engines were good and each model provided better power than the last and some improvements in technology. They are very durable, have minimal to moderate repair issues, and get good fuel economy. The one problem that comes to mind is the later Powerstroke engines could fall victim to the CPS (Crankshaft Position Sensor) failure.
The 6.0L has lived a rough life and while some of it is due to design, a VERY LARGE part has to do with lack of required maintenance, and the introduction of the engine when 500 PPM fuel was still for sale. Yes there are some lemon like engines out there, but the vast majority that have/had problems simply suffered from the design flaws that have been corrected, and POOR MAINTENANCE (notice the trend in my description) . This engines major problems are the EGR, the head studs, and injectors that are sensitive to clean fuel and oil. This engine can be very responsive to power upgrades, and can be reliable if you do your research and can find a good one that has been maintained properly. Fuel economy is slightly lower than the 7.3 because of the emission systems installed.
The 6.4 has been a good improvement but suffers due to the DPF regens killing fuel economy. There have been some EGR cooler issues as well as some injector issues but they seem to be fewer and farther between them.
As far as the 6.7, you are in the same boat as the rest of the USA. We are waiting to get our hands on it and see how it does.
Anyone is welcome to elaborate more on my info, I simply put in words what I could think of right now. If you spend some time surfing this forum and some of the other ford diesel forums you will be able to develop an understading of which powertrain best fits your needs.
