Question on the exhaust manifolds. Are the outlets close on the 340 and 350? In other words, would a "Y" pipe fit a 340 and a 350?
Not very well! So in 68 the LeSabre was only offered with single exhaust- even the "400" option. I purchased a 66 dual exhaust for a LeSabre 340 and made it work in the 68 with 350, but the driver's side is decidedly different in angle and length. Passenger side was pretty close.