I’ve read of 6-speed conversions of M104s without fabrication but I’m not an expert.

I don’t know Blago but he says it’ll work - http://www.benzworld.org/forums/w124-e-ce-d-td-class/1481405-any-m104-autos-5-6-speed.html#/topics/1481405?page=1

Google says there’s such a conversion in this thread - http://forums.190rev.net/showthread.php?35638-Project-Indecision-Now-finally-with-V12-T56-and-a-Turbo

Sixto
98 E320s sedan and wagon