The reason theO-360- A4K had a special fuel pump situation was due to interference of the fuel pump with the carburetor after the newer longer style fuel pump was introduced. So for the pump to fit with the HA-6 carb the bottom of the pump was rotated to make it so the pump woudn't inerfere with the carb. But the fittings on the pump became very close to the engine mount structure used in the early aircraft applications. So a variety of plumbing issues resulted on the Gruman American installation. It had nothing to do with anything else on the engine . So, if you convert the o-360-A4K engine to an IO-360 and leave the original sump on, you would need an adapter between the sump and the servo as the mounting pattern for the o-360-A4K Ha-6 type carb is different than the servo bolt pattern. That adapter would move the fuel servo aft and I think would reduce the concern of any interference issues with the servo and fuel pump. If you changed the oil sump to either a forward facing IO type sump or regular O-360 pointing down sump, you would use the same high pressure pump that every other IO-360 uses, without any modifications necessary. The warning about whether the new style longer pump having interference issues was due to some aircraft having cooling shrouds over the pump with a duct going to it. The interference was with the shroud fitting over the newer style pump and not with the pump and any other engine components. Hope this helps!
Good Luck,
Mahlon