If it works OK just keep topping it up. We had a Blubird back in the 90's and it leaked for about 5 years but never gave any concerns and the only costs were the fluid and engine cleaner for the drive.

While you will have to narrow it down from the rack, the hoses, the pump, the reservoir or the cooler, all the bits are cheap on ebay and easy to fit. Only as a last resort would I use snake oil, but the Lucas one does work and as well as stopping leaks, is a good general conditioner that stops some systems moaning, like Jags for example.