i am by no means an expert but what i do know is that the toy frequencies are very unreliable and can and will make the r/c car act up in ways that it could be uncontrollable .my suggestion is if you value the car and want to run it ,i would recommend changing the electronics to the more modern one with the 2.4 ghz radio system .one thing you don't want to have happen is to be out somewhere running the car and experience interference and have the car take off uncontrollably and smash into something or someone.the value of the car is priceless to you and from the sounds of it you have no plans to sell it so i would change the electronics
that way you have piece of mind and feel somewhat safe with it (nothing is 100%foolproof) the only time when swapping out something would be an issue is the drivetrain.if you were going to put a hobby grade powerful motor in it you would have to be careful if you are going to use the original drivetrain .you need to get a motor that the drivetrain can handle .i have a kyosho vintage 1966 427 shelby cobra and i was going to put a brushless system in it using the original axles and such and was told that the motor would be too powerful for the drivetrian and since the parts for it are no longer availible to fix my car i decided not to do it.i do have a batmobile that i put a modern radio and receiver with digital steering but kept the drivetrain (well my hobby guy did it for me)..sorry for the long explanation hope this helps you decide ...good luck