I am contemplating replacing my L48 and 700r4 setup with a late model 6.0L or 6.2L Vortec with the 6L90 six speed.   I did the TH400 to 700r4 swap a couple years ago and it only took me five days.  I Know that I will be modifying the cross member and tunnel some what.  The  Vette is a restored driver.  I intend to set the original engine off with the original TH400 and keep it in storage.  Have any of you seen any attemps to make this exchange?  I have seen a couple of early Nova conversions.

  Are you refering to a Vortec ( Standard Smallblock Chevy) or the new LS Series Engines? (97 and newer)  If you have a 700R4 allready I'm not sure Your going to gain that much going to one of the newer 6 Speeds. If you plan to run a Motor with much Cam in it it may not be able to run down the Freeway in 5th or 6th anyway.

I am referring to the SBC vortec's cast iron block with Aluminum heads (2007-2008).  The gain is 1st gear  4. versus 3. and closer ratios. Overdrive is .67 versus .7 in the 700R4. The real gain is FI smoother performance.  Thanks for your comments