I have a first gen Hilux that I believe to be early seventies based on the funky hood turn signals. It originally had an 18-RC engine that was seized so the owner removed it. Due to 18R engines being very scarce on the east coast I instead am trying to swap in a 22R engine I have. The 1986 22r came with a 4x4 transmission mated to it (no transfer case) so my original intent was to use my stock 18-RC 4 speed manual. The issue is it does not have the same splines on the input shaft that the 22r trans or clutch plate do. My first fix was trying to swap to an older clutch disk for a 70s celica but after unboxing it revealed to not be a match either. Is my original transmission a weird 18R special one off(it's an all steel with a "side draft" [my term not one I've heard used]), does the celica use an enlarged clutch disc spline pattern (although it was advertised to work with 18R) or finally is there a way I could purchase or fabricate a spline adapter to "thicken" the 18R trans input shaft into fitting into the 22R clutch disc?
P.s. If I do have to throw in the towel and purchase a new 2wd trans what is the difference between the 22r W56 short box and long box?

Thanks
Joe