Just finished my own P400 swap in my 95 burb. I only have about 2300 miles on it but so far everything is good!
The P400 is not an exact "drop-in" replacement. If you have 4 wheel drive you will need to have the oil pan modified. The bell housing bolts are metric. I also had to find new exhaust manifold bolts, the new manifolds were just a bit different.
At the same time I also changed engine/tranny mounts, installed high output water pump, installed dual thermostats, new exhaust manifolds, timing gears, marine injectors, and new oil cooler.
I purchased the engine from Penninsular and they have a process to modify the oil pan. The pan is made from cast aluminum so unless you are good working with that I recommend having someone else do it for you.
I am also running an ATT with a Heath tune.
I just returned from a business trip, 1900 miles, the engine performed great, no problems. The engine oil still looks clean after the trip!
If properly set up the p400 will have enough power for the normal suburban owner. The p400 is rated for more horsepower and torque than a regular 6.5. Since my only horsepower/torque improvements are new tune, cold air intake, 4in exhaust, and ATT I do not think I will be in any danger of overloading the engine and breaking something.
If you need more power you could order it with 18 to 1 pistons and crank up the boost and fuel.
It was a lot of money, especially for an older vehicle, but there is nothing like a diesel burb going down the road
. Would I do it again? Yes.
Brian