Well a couple of things

#1: 115 car is far superior IMHO . Handles way better not to mention looks a lot cooler than the 123.
#2: Quick lesson 300D-3.0L 240D 2.4L 220D 2.2L you get the idea..So anyway yes the 240D is a bit slower at 60 some odd HP depending on condition but I've seen 240's that run just as good as a 300 hoopty if that is what you have.
#3: They will all cost you money. Something will always go wrong with these cars. They are only affordable if you can do the work yourself. Now that you are here log onto the DIY pages and save yourself a bundle.

Welcome to the forum and pick up the 115. If you are looking for a car to work on though the 115 is a bit tighter there in the engine compartment and parts can be a tad bit more difficult to pick up...but not to bad as the engines are 99% the same. It is still a 616, 617 so you are good to go. Ohh by the way the 240 is a 616 and your 300d is a 617

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76 300D 130K "Stella" (Sold )
74 240D 299K (Donated to Highschool For Senior Project WVO)
83 300TDT 290K (My one and only)
Sanford, NC