that's really ambitious for a "first" build. get a jdm long block and swap it in (engine + trans already assembled) and drive that for a bit. then decide about the transmission swap. swapping from auto to stick seems quite complicated and then you want to go RWD, I think you're asking for problems. the reason G20 rocks is because as stock, drives great for 4 cylinder banger. if gonna do that much work, why not redo mounts and go 6 cylinder from other car? or, just spend the money and get a different 6 cylinder car with rwd already?