Okay,
I used to be the general manager for a cummins dealership here in Lincoln NE. We we're a mid-range industrial dealer. Did a lot of repowers in equipment. I've owned many dodge diesels and love the cummins for everything. Decided to take out the 360 gas with the 4 barrel because of terrible mileage. I found a diesel 727, and put everything in. It runs good. Plenty of power for a unloaded truck, or very light load. My main problem is that I run out of gear. The 727 3-speed with 4:10 doesn't work very well. It is my "farm" truck. I use it to go between my house and the farms (roughly 30 miles) Many times hauling firewood in the back. The truck will only do about 62mph. The mileage is good. Always over 20mpg. Which is about double that of the 360... . I really just wish now that it had the 5-speed or an aux-overdrive behind it. I think it would get mid-twentys with the overdrive. The main thing to consider with the 4bt is the vibration. It is not a smooth running engine... . I couldn't put in the industrial balancer because it requires the deep sump pan which I couldn't use because of the front axle. All in all it is nice, but just a bit shy on gear. You should see people look at me though... Sounds like a tractor going down the road. It just fits me. They used to call me the "repower king". That was another day in a different time.
Now I've rambled enough. Hope I've answered your questions. If you can ever get your hands on the old "salesman handbook" it will tell you everything you need to know on doing repowers. All flywheel housing, flywheels dimensions differences etc, etc. Cummins used to have a program called powermark in which they came out with their own kits for repowering. That is where most of the 4bt repowers came from in the p30's. Okay I'm going to stop talking. I've already said too much.
Pete
Attention: TDR Forum Junkies 
...
