If the servos you plan to convert were used on older AM systems, they may have been designed for a 1.3ms center instead of the now common 1.5ms center pulse.
I have seen once where a servo which had it's plug converted would act normally until requested to move to the extreme associated with the longest position-pulse. It would then move to the opposite extreme. In this case, it was used for a throttle servo. It worked fine untill full throttle was requested... Instead it closed the carb completely. Imagine if that were on the elevator: "Gently upply up elevator till it takes off..." then when you give it full up elevator it dives instead.
I would go ahead with the conversion, but test them
thoroughly! If you radio has adjustable travel rates, turn them to maximum for testing.