OBD1 PCM interchange/compatibility, 5.2 vs 5.9

Hey all. I'm wondering about the negative effects (I've read fuel curve differences) of running a 5.2 PCM with a 5.9 engine. '92 Dakota 5.2 donor w/a 518. Motor was junk, hence the 5.9, and I do have a 94-95 5.9 PCM. I'm trying to figure this out because of the wiring change between the early 2-wire VSS, which also runs a speedo cable, and the later '93(?) up 3-wire no cable version. The combo unit works off sensor ground and speed signal to the PCM. The later unit, however, is wired to the 8v supply (in series w/the cam and crank sensors), the sensor ground, and the speed signal. Nutshell- if the newer 5.9 PCM won't recognize the 2-wire VSS, what issues am I going to see with the 5.2 unit?