Hi Matt,
I see you’re in WI. I’m in WI as well in Hudson, near Minneapolis/St. Paul.
I just did an engine swap from a donor 1990 300E to my 1989 300SEL. The engine management system changed even between those two years. I had to change out sensors on the donor, 1990, engine to make it compatible with the 1989 management system wiring. I can’t imagine moving a 1995 104 engine to a 1986 103 engine wiring harness without turning it into a real science project. Additionally the cooling system is all different; the exhaust system is all different. I think the ’95 would have a blower motor for a dust filter so you couldn’t even use that. I'd wait and try to find a ’86, ’87, or ’88 donor.
Outofspec