Propshaft flange bolts

Hmmmm. Feeling like a muppet :oops:
Busy removing u/s engine from '89 280GEL and came to conclusion that 'box needs to come out as well, then separate them.
Tried to undo the small output propshaft from the input end on the transfer case, christ what a nightmare the little bolts and nuts are to get off (had been soaked in plusgas (& 3yrs worth of engine oil :cry: ). Seems like they are fitted to butt-up to the propshaft, therefore impossible to get a socket or ring spanner on. Cannot believe mercedes would design something that could only be removed with an open-ended spanner, without much success.
Am i missing something here? Have one stubborn little ***tard left which is rounding off nicely :oops:
Is there a special tool for this job? Or is one supposed to cut them off & use new?
Yours, confused and bruised of Camberley (and frozen solid :( )