From what i've seen on forums and in a friend's scrapyard IMO apart from the chassis rust probems and a bit less confort the D2 is a newer and more reliable vehicle than the P38, it's very important how the owner took care of it*which is valid for any vehicle). (i'm comparing ES modells with EAS/SLS and other enhancements not basic modells on coils). The D2 has a better engine and stronger transmission due to the LT230 which is way better than that Borg Wagner box with chain. Even if the Td5 engine has it's specific problems if it's well maintained and correctly used it's almost bullet proof compared to that frigging BMW engine which has more issues, the EAS and BEcM are even more complex and harder to diagnose than the SLS and BCU... at least that's what is saw with my own eyes though i might be subjective cos i'm a complete D2 enthusiast.
As the OP was talking of getting rid of a V8 and replacing with a V8 your comments on the diesel engine aren't really relevant.
As for stating the D2 has a stronger transmission is stronger, well its the same gearbox in auto guise which I would suspect the V8 to be and many TD5s.
The only difference is the TB. Now as much as I admit the LT230 is a pretty much bullet proof box the BW in the RR is not bad either. One could argue we see more needing to change output seals on LTs than BW??
I have not heard many RR owners having issues with theirs. I certainly haven't had issues.
Granted they operate in different ways but a D2 without a CDL is not going to be better than a RR ever.
The Diagnostics you use for the D2 are not much different for the RR so I don't see the comment of more complex as correct. The stuff you know about the D2 is second to none for me, I read your answers to peoples problems and see you know your stuff on the D2.
But then there are people like you on here, who know there way around the P38 issues too.
When you know, its easy, some know the D2 some know the P38.
The thing is its the maintenance that makes the difference. Regardless of name badge.
J