Your best bet is to read through the swap threads on AudiZine. Unless you have a 4Mo, there's little point in the swap.

 

My main goal is I want to v8 swap my passat it's a fwd but I wanna convert to rwd if possible using any engine that can be a simple instal even with fabrication I can fab shit if I need to but I really wanna v8 swap it

 

... and to add on top of what has already been said.
You'll want a 4motion manual trans, the auto box won't hold up very well to a 4.2l.

At this point, why not just go with an Audi 4.2 A6?

 

V8 will not fit . Waayyy to long

 

I want to say it's been done by somebody. I mean, it fits in the B6 S4 and the engine bay is roughly the same size. Even the A6 and Allroad.

 

Even the complete frontend of a C5 A6 differs from the standard C5.
The V6 Biturbo of the RS 4 fits tight.

 

So what about a 350 small block? Lmao yall don't think I could stuff a small block Chevy under the hood? If the 4.2 is too big I know a 350 is fairly small I have one. I've got an old scotsdale that I wanna rebuild but I wanna put a bigger engine in that so I will have a spare 350 laying around.

 

Put the V8 in it that has the timing belt on the front of the engine, but it probably won't fit because it's kinda long. The ones with timing chains between the motor and transmission would fit, but they have their own special set of issues you would probably rather not deal with. I don't get how a german engineer would think oil pressure activated timing chain tensioners buried between the engine and transmission would be a good idea. I tried to find a pre-oiler system for mine before it went kachunkety clunk, but there is no such animal that I could find.