The only weak link that I am aware of in the R154 is the thrust washer. Google "R154 thrust washer", you should find several links that will show you what goes wrong.
I am convinced that since the bearings on the mainshaft are not preloaded and there is clearance for the gears to move, when the clearance get's bigger due to wear, and the clutch is dumped, first gear hammers the thust washer and shatters it. But, that is just my theory. So, I think that if the tranni clearances are kept tight, and you don't do any high rpm clutch dumps, I thing it should live for a long time. I would run it in a heart beat.
The 6.1 is just too sweet. If I had the cash, I would do the exact same thing.
