Are you converting to rear wheel drive?

 

Probably not.

 

I think I saw this done on a Discovery Channel TV show... We're talking about a C30 with a 5 cyl white block and FWD right? If you are asking about how to install a V6 like in your mom's 84 Buick, then you need to measure from the radiator to the firewall. If not enough room then its either move the radiator out, get rid of your AC set up and maybe move the brake booster. Oh shoot, I forgot you need a transmission and there's no firewall tunnel so its time to torch up the firewall and floor panel to import in from a car that uses a RWD transmission. Better go back to the drawing board and try see if you can fit the V6 transversally to mate to the Volvo transmission. Even better is to realize that the 5 cylinder Volvo turbo in the C30 can be tuned to make more HP than any V6 you'd be considering installing - 300HP is in easy reach with a $2500 budget for ECU, larger injectors, after market intercooler, upsized turbo, 3 inch downpipe and exhaust and various boost management parts.