I wish I had contact information for a guy in Salt Lake City who put a 408 in his 62 Valiant. It was an absoluteley sanitary swap. I talking to him though... He removed the heater and replaced it with a heater setup from one of the aftermarket A/C companies so it all went under the dash. He also found a piece from some car in the wrecking yard which provided perfect distributor clearance in the firewall that he cut and welded in. He had a 1964 cable shifted 904 from a '64 Barracuda well built with alto red, kolene steel and a transgo kit. He said aside frome the usual motor mount issue (he fabricated his own from the 64 Barracuda parts car) and a dropped center link, also from the 64 v-8 parts car, there were not a lot of issues. As with all early A-bodies, exhaust was his biggest issue but he lucked onto a set of early Spitfire headers and they fit like a glove. Just the usual notch in the transmission crossmember made easy work for 2-1/2 dual exhaust. He had done the front disk swap from a '73 up and put a 3:55 8.75 a body rear in it. He shortened the driveshaft from the Barracuda and retained the ball and trunnion front u-joint. (which he said had held up well on the street and through several 1/4 mile passes each year) He also modified the radiator core support to provide clearance for an Afco aluminum Ford racing radiator and a Taurus fan but stated that was not necessary if the /6 radiator is replace with the v-8 radiator.
Aside from heater/firewall clearance it appears to be a very similar swap to any early a-body. There's a ton of info on FABO re. v-8s where a six was in early A's.
Good luck with your project and please keep us updated with photos.
