I don't think it is a case of people NOT wanting to help you, but rather they CAN'T help you. Most parts people don't even know about the different options available. They know that in order to get the correct part for a customers engine, one that is either bought new in a vehicle, used in a vehicle or reman from ReCon, an ESN is needed. That number will show how the engine left the factory when it was put in the vehicle it was designed for or designed to replace.
I worked there for 30 years. I remember doing re-powers as far back as 1995 , IIRC, the first ones were these little funky trucks that So Cal Edison had that were purpose built for cleaning components up on top of the power poles with some sort of high pressure hot liquid, 12 of them I think. They had Deutz 6 cylinder engines in them and they wanted 6B's. When the engine for the first one got there, it came with no flywheel housing, flywheel, front mount, fan drive or idler/tensioner, alternator bracket, coolant inlet, A/C mount, air compressor...because that drives the power steering and Deutz couldn't tell us what type of drive was used.....basically it was a long block with some extra parts on it.
When I saw the engine, I went to the Engineer, at the time it was a guy named Bob Kano. He was one of the BEST engineers I had the pleasure of working with. He explained to me the process of finding out what pieces parts to get based on all the things like drive angle, placement of the cooling package, cooling rejection needs, drive type, etc., and led me to his library. His library was a wall, filled with these little 2 ring hard cover binders, option books. These books had every part that Cummins had ever made and created a p/n for, for every engine made at the time, from the little A series used in UPS package truck and generators, B, C, 504, 555, V8 300, 903, 10L, 855, K19, 38 all the way to K50.....that was the biggest engine Cummins made at the time, Haul Trucks and prime power. Every option had techinal drawings, measurements and a list of other otions that would work with it.
I was tasked, on this first re-power, of stripping the old system out, putting the new engine in place with no ends on it, setting drive angles, finding an envelope for the cooling package, measuring and then spending days looking through the option books to see what Cummins offered that would work for this application to make it fit in the package/envelope we had to work with. Cross members were moved/removed, transmissions were changed in favor of an Allison, PTOs added, intake and exhaust manifolds changed due to the envelope the engine HAD to stay in. I think the first truck was there 5 or 6 months. After we figured out what the engine needed from the factory to mount it into the chassis, the rest came with all of the parts I put on the 1st one and time was cut to about 3 weeks.
Now, all of those options are in a database in the Cummins system. HOWEVER, the components are current production only. The engine you are working with, in Cummins eyes, is a dinosaur, not in production, obsolete. I used to get yelled at, well mostly just a good talking to, when at the end of my career, the engineers would tell me that I had to "make it work because there is no other part available" I would go back to these books, yes they are still stored in a box I left at the shop, find a part from "the old days" Knowing it would work on the newer engines, order and install the part and it would work perfectly without the engineers approval.
Now, though, as I was in the retirement phase at Cummins and Cummins in their "want control of everything" ways, have limited the people that have access to the option database. When that happened, it was a severe blow to how I did my job, it increased times, the amount of incorrect parts ordered and returned, forced fabrication of components which means if it ever failed, the end user is SOL, etc. That is one of the reasons I left as early as I did.
Enough. But I do remember the next repowers. Disneyland Monorail tow trucks! It was cool, after the re-power of both, I got to drive them up on the rail! V8-470 out, tier2 6B in.
( Mine measures right at 5 1/2!) Soooo Back to square one. I can't see a dual disc clutch pack is shallower than most clutch packs for a manual. Starting to think that I got another piece of Scrap from Active Truck Parts in CO (all the other parts went to the metal maggots! Don't buy from them!) in the form of an out of spoec flywheel. As par the course I will keep everyone informed as I am not the only one who wants to run the BEST transmission (Eaton FSO-6406/8406) behind a 6BT!