There are no mods necessary to place the bouncy seat base on the passenger side. The adjuster knob clears everything. Those folks who've switched the knob sides did so for aesthetic reasons. Second, the 6-bolt frame is simply a 4-bolt frame with two extra tabs welded on, just cut them off or bend them out of the way. Simple.

The only way to get you a factory 4-bolt unit with a right side knob will be from an RHD Mitsu.

1987 Raider - Roxy
1988 Mighty Max 2.6L Turbo - Pearl
1997 Mountaineer V8 - Freddy
2000 Excursion V10 - Freya