The main concerns about the Northstar being installed were if the stock puny transmission in the VX would survive without the engines power being substantially de-rated. A TH400 is a pretty compact transmission so it ought to fit. Ford stuff usually=more money than GM with less of an active aftermarket utilization. You can find GM LS series engines being converted to power just about everything on the planet that moves.
Would the th400 link up to the 3.5? My current oem tranny is not doing so well and I am looking to replace that first for the time being. What about the 4l60e will that link up to the 3.5 as well?