I would say without seeing the PS box, that you are correct to think it all has to be "re-engineered" to get it lowered. To start over would be a safe bet, and to go with the MII, there are others on here who can help you. To keep the engine in, I dunno, but oil pan clearance would be an issue. ONe thing to note, that when you buy other people's projects, there's a reason....they did something wrong and want to unload it....the saying around here, is "don't be that guy."....we like to see them finished.

Good luck