VHF: power resistor to replace dummy load
The inductance of the resistors will give you a lot more trouble than the wiring.  Carbon resistors can work well enough here, available in 2W size (if they still make them!)  Build up your load by paralleling them.  You may be able to tune out some of any resulting mismatch if the PA (power amp) has adjustments for it.  In an extreme case, build a transmatch to match it.  In practical experience, "close enough" and "for short periods" was good enough and didn't harm the amplifier.