I posted about this in his for sale thread in the parts subforum of this site. The 603's use the same size overflow valve as the 61x engines. The long bolt is for the 606 engines. I assume he has not updated his website to reflect that.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]