Not really sure on that one but I THINK signals were pretty similar back in the day. What that translates to is that if you pick up another (matching number of channels) receiver that is 27mhz, you should be able to use it... But let's get real here for a moment... I think you would be WAY better off upgrading to a 2.4 system! Let's face it, that stuff is old and beat, even if it's cool and retro. If I were you, I would be looking into a system that can be used in all my rigs. So if your max # of channels used is 4, a 4 channel or higher radio... Make sure it is capable of running digital AND analog servos so you can upgrade servos as needed/wanted. Most radios are capable of a 10-20 rig memory, so you can store each kit in the on board memory of the radio without having to go thru all sorts of setup etc... They aren't THAT much money and the adjustability, reliability, range, features, waterproof components, speed... ETC... Is just without question, hands down a better option for ANYONE in RC who isn't doing a retro/resto project. Personally, I would buy 1 GOOD system that will carry you for a long time to come and be done with it. From there, if you choose to, you can upgrade servos... You WILL have to purchase new receivers for any rig you have that does not have a 2.4 system that is comparable with your radio of choice. So yeah, some investing to do but don't let it scare you. Systems can be bought for low dollar and receivers can be bought as 'knock offs' for short money which work just as well according to the ppl I have talked to and reviews I have read. Servos are really the only somewhat pricey thing you have to concern yourself with.
(esc's may or may not work with all of the features of your new radio as well. If you're using electric cars, research that as well)
Oooooooooooor... Just look for another antique receiver and hopefully it will do the job for you.