Everyone wants to know if it will "fit". Undoubtedly it will fit, but the question is whether you can get it to work, at a reasonable cost. A "93 104 300" could be a CIS engine (300SL), an LH engine (300SE) or an HFM engine (300E). You'd be in the best shape if it was a CIS engine but it would still be a big project that would require transferring many components from the donor car and considerable experimentation and trailblazing. If you are not capable of tackling it yourself I would get a shop to quote a fixed price for the project, which many shops would not do.