1973 THM 350 Governor nylon gear failure

[jcdkool]

The 1973 THM 350/V8 350 replaced a 3speed manual/250 L6 in a 1967 Chevy C10. 1973 power train/plant was last used around 1990. The C10 has been on the road for three months but highway mileage has been kept to a minimum. Took C10 on an 80 mile round trip but only made the first 40 and only had 1st gear. Speedometer did not register correctly and engine rpm’s seem to be high in 3rd gear. The governor nylon gear failed. At the parts store/trans shop the manager showed me a torn down transmission and said the gear will fail again because of movement in the output shaft. I related the failure mostly to age but what the manager said is logical. Are there other reasons for the gear failure that I need to check in the drive shaft/rear end/wheel size/tire size, est? What should I do about the parts of the failed gear thats still inside the transmission? Any advice on this subject will be greatly appreciated.