1994 Pro50...Options?

[multiboat]

My son snapped off his Pro50 lower unit after having purchased it in Feb 2012, so is still paying on it and now he's found out that the lower unit is unique to that year (1994) and the replacement cost is too high . What options can anyone give us?
- Are there certain parts I could replace that would allow the various lower units I see for sale from the late 80's to early 90's lower unit fit on it?
- Anyone know what makes it unique?
- Is there a conversion available?
- Do we part it out?
- Can the 50 even be put on a 40, if so what years?
Thanks in advance.

[boats.net]

91-93 were different color, 1995 and up were several changes in gearcase but would work.

[multiboat]

Thanks. Is there a site I can go to find out what exactly the differences are? Shafts, # splines, etc?