I would swap an S52 from a 96-99 M3. 318ti are configured into 4 packages; base, active, sport, and clubsport (1995 only). Doing a search will inform you of the differences which include suspension, exterior styling (M tech bumpers, mirrors, moldings...), interior (leather, cloth, two tone), and a few other bits.
If you plan on heavy modifications, just go with a base package as you will be changing everything up anyway. Good luck and keep us posted on what you get!!
I may have a lead on an S52 engine and trans or a little over a grand but I have no idea what the condition is.... I'm gonna investigate __________________  |