Sure, i wouldnt call it complex just highly time consuming.
You can either produce a mid engined affair ala clio v6 with the engine in the boot and basically transplating the front end of the donor vehicle, using subframe, fabricate some turrets, lock the track rods and ideally make beefier ones.
Or a front engined layout which would require fabrication of a transmission tunnel, custom prop, rear axle either live or independant off a donar car, remove boot floor and fab up some turrets and make sure the position of the diff is true, level and parallel.
Not something i would take on if you have to ask these sorts of questions, its not a matter of just boofing in an engine....well you can but it probably wont drive straight.
And a bike engine i wouldnt bother with unless you can get total vehicle weight down to about 500kg if your running a chain drive, 650 if your running a shaft drive setup......and bike engined projects require really expensive running gear setups, i'm talking thousands just for a diff.