It could be also a simple layout on PCB and if distance is small it might even don't care at this frequency (assuming the signal source and signal load are not sensitive to impedance variations).
My suggestion is to use transformer type. As ur frequency is just 400~500 Mhz.
If u r ready to waste so much power just to match, then resistive is ok.
All VHF /UHF 300 ohm to 75 ohm convertors r of transformer type.
Could you give a picture of example 75-50 ohm coverter of transformer type?
if the frequency is higher than VHF/UHF, what kind of 75 to 50 ohm converter will be better to use?
For a single frequency a LC pair will perform this matching but over a wideband, "Wideband Ferrite Core Transformers" must be used to convert 75-50 impedance scaling..
Resistive dividers are very lossy..