Forget classic oil cooled dummy loads and make a power chip resistor based dummy load by using a 50 ohm power resitor on a heatsink. For a short time loading you can use a smaller heatsink. For higher duty cycle use a bigger heatsink or a fan cooled heatsink. Bolt down a 50 ohm power chip resistor to a heatsink with a thermal paste and install a RF connector of your choice. This way you can easily make a good dummy load from HF to VHF.