Economical Fix
BudI replaced both the transmission and throttle cables on my '80 Cat 30. Like you I had difficulties finding a match. No marine dealers I talked to could tell me what I needed for replacement cables. The cable numbers could not be cross referenced with existing cable manufacturers. I removed both cables and took them to a truck supply company. The company was Inland Truck Parts Company in Tulsa, OK which operate in many parts of the US. They made me replacement cables the same type specifications as the best quality from west marine. The cost was less than 1/2 the west marine cost, and I had the replacement cables within two hours, the fit was perfect. West marine had a 1 month delivery time and would not guarantee fit. If you don't have a ITP supply house I am sure that other supply houses for large trucks in your area have the same capibilities.Good LuckBob