I don't think 70 F100 comes with a 390-its all 302 as far as I could recall unless modified.
I had a 75 F250/390 its beenlong long time if Ican remember its something do with the bypass hose and the baffle plate under the intake.
Also in the mid 70's 460's on the F250
Also the 351's C/M/W came in.
BTW if its a 390 make sure you put the bypass hose on the intake before you mount it otherwise you gonna have a hard time connecting it if you go the other way BTDT.
Friday, October 5th, 2007 AT 4:39 AM