Originally Posted by JimFreeh

Subframes are the same with one exception: You will need to drill access holes to get to the W107 engine mount. Good thing is that the position is already stamped... The 85 and earlier W107 is the suspect one. The 86 and up 560SL had the factory reinforced subframe. The issue is the lower control arm rearmost mount, it can tear from the subframe.

I used a W114 subframe when I replaced the broken one in my 84 280SL. The MB kit for the subframe was around $100. It consists of gussets that you weld at the suspect mount to reinforce it.

If I were to install a V-8 (M116/M117) I'd make the above mods, and figure out which trans mount frame piece to use. The rest should be pretty easy..... yeah....

Jim