There are tons of DB era IV sleeping car photos here, and the passenger cars you mentioned appear somewhere in some combination:

https://www.wagonslits.d...bb2/viewtopic.php?t=2160

The German sleeping coach fleet was assigned to D.S.G. (Deutsche Schlafwagengesellschaft). There were a number of coach types, including a few pre-war and post-war designs.
The most common would have been the WLAB174/175 type. In the early 1970s, the coaches were transferred to the new Trans Euro Night (TEN) Pool. The T2S (WLABsm166) was put into service in the mid-1970s.

As you are modelling the earlier 1/100 models, the T2S WLABsm 166 was the model made by Maerklin in that scale. The first models were not equipped with close couplers and had extended spacing between coaches (4150/etc).
The second generation models had a shorter coupling shaft and already had the offset bogies (4182). Maerklin later released a DB model with close couplings under the number 4240. It represented the later appearance of these coaches.

Maerklin later released an Auto Train set, which would make an ideal addition to your 429X coaches. The set was available as 42999 and included 2 T2S (WLABm166) sleepers, a Bcm UIC-X couchette coach and a car carrier.

If you want to make your consist more interesting, you can add a Swiss couchette (4268), Dutch NS couchette (42696) or Belgian couchette (4274) to make it an international consist.
Roco had models of the earlier WLAB174/175 type cars. I have this model and a couchette in SBB 90/2000s colours (Era V)

Regards

Mike C