The issues are basic voltage regulation (poor), and voltage regulation as drop under local load.
The load type is probably not nearly as important as the load amount. No reason at all why a 3 phase converter cannot be used, up to the capacity of the local transformer. Likely the power company has some guidance on what loads can be put on the line, and those limits would be what you need to follow. References I found even mention converters for local 3 phase
8 HP is roughly 8 kVA, or a bit more, so the local transformer needs to be somewhat over that to supply starting surges. a 25 kVA transformer , if it fairly represents the supply capability , should work. But with SWER, starting that motor is likely to produce very significant voltage variations, mostly voltage drops.
Once the power arrives at the facility, there is no difference between SWER and regular power, other than the poor regulation, and higher source impedance. Whatever kVA load you are allowed can go to lights, a converter, motors etc, etc.
The best converter is likely to be a VFD, of a type including an input power factor corrector. They are not yet common, bit do exist. That will allow the most power from a limited source, and will avoid starting surges that pull down voltage.
