Negative, that looks entirely insufficient.
Bolt lengths are 26 cm and 30 cm, or about 10" and 12" in US Customary. They don't need to be threaded the entire length, just the last 50-75mm or so.
As I recall I paid a little under $80 for the set, which at first seemed a tad excessive so I thought I'd make a set as I have a machine shop, but after totalling materials and an estimate of time $80 started to sound quite reasonable. You can fabricate a set cheaper, but not by an enormous amount so I would recommend just buying a set. If you happen to live in eastern Wisconsin or central Indiana I can arrange the use of a set for a couple of weeks.
Here's an image of my set to help you get an idea of how long they are.
View attachment 66242
I have read of alternative methods of doing it that don't involve the lowering bolts, but I can't recommend them as the alternate methods I have read leave half of the subassembly unsecured.
I find the bolts have saved me more than what they cost in hassle and time, which for me makes it a no-brainer.
Edit: I presume it's apparent, but I think it's worth stating that the lowering bolts go in with the car on the ground and the body is then raised up off the subassembly.
Edit2: I see they're not as easy to find now.
Full spec I have on them is as follows:
450 589 00 62 00
Bolt lengths are 26 cm and 30 cm. Thread size is M12 x 1.5. Grade 8.8. Threaded length 50mm
If you go the fabrication route and don't have the tools or perhaps skill to make them yourself, I would talk to a local machinist or pop over to hobby-machinist.com and see if you can engage a local from there to help you out.
Edit 3:
W450589006200 - Record Release Bolts For Lower The Rear
www.mbonlineparts.com
Looks like MBOnlineParts still has some, and the price has gone down. It would seem there's a "W" in front of the part # sometimes?